I have been doing some searching and I have found some sources and possibilities. I am waiting for responses to the questions I sent to the Customer Service section of a few sites.
Here are my results so far. I will be editing this page as I get further information.
NOTE: When I make the edits, I will date and have them enclosed by parentheses. Make sure you skim the page each time you look at it as I intend to try to keep the same topics together, rather than adding new information at the end of the page.)
The Finnish article is found here:
The English article is found here, courtesy of Cheryl Rodgers: http://www.aquatic-gardeners.org/articles.html
(down at the bottom).)
A link to Jyrki's 2006 First Place entry using his cast rocks entirely: http://showcase.aquatic-gardeners.org/2 ... l=-1&id=26
In thinking about the use of a solvent to dilute the Vaseline I have been getting uncomfortable. Mineral Spirits don't evaporate quickly. Some may become incorporated into the casting. Jyrki may have used a different solvent. I am not sure. He is very concerned about the use of food safe products; maybe he does have something different. There is most likely going to be a layer or spots of Vaseline left on the outside of the casting. Thin yes, but there is probably a good substitute on the Alumilite website. I haven't looked at them in a lot of detail yet. But they have casting resins, mold making resins, mold releases. All we need. http://www.alumilite.com/
I think I responded to Jyrki’s reply below on March 13 before but must have deleted it when I was editing. He says he doesn’t have any problems with Vaseline or Mineral Spirits remaining on the casting. As I have been reading about the Latex Rubber on various sites I have seen warnings against the use of Petroleum products. This concerns me so I wrote to Jyrki concerning it. I have edited both my email to him and his response, but I haven’t changed the message sent or received:
My subject line leads me to the next question. I have refrained from posting it until I spoke to you. While reading about latex rubber I remembered the warning against using Vaseline on latex rubber products like latex rubber gloves used in medical examinations. The doctor uses a water soluble lubricant. Some of the latex rubber companies I linked to warn against the use of Petroleum products on the latex. One said a soap solution sprayed on the rock when dry will be a mold release. But one did recommend using Vaseline on the outside of the mold prior to removing it from the casting. Maybe they were talking there about other materials besides latex.
I think for long term life of the mold, it would be best not to use the diluted Vaseline as a mold release. I could easily see selling some of these rock castings to the local fish store to recover some of the money invested in it, at least to get free rocks for ourselves! I wouldn’t want to shorten the life span of the mold.
I have used my moulds several times, 4-6 castings per mould and the Vaseline mixture hasn’t done anything bad for the moulds, except once. Last summer I made some castings outdoors, because it was warm and sunny weather. So I put the Vaseline mixture in the moulds and let them stay - but the moulds were in direct sunlight. I made the castings and tried to release the mould from the hardened stone casting, I found that the mould had melted a bit and stuck to the stone. The warmth and direct sunlight made that happen. The Vaseline mixture reacted with the latex mould and made it too soft and a bit like bubblegum.
So it’s safe to use the Vaseline mixture, but in normal room temperature and not in direct sunlight.
Again, Sune Holm uses it too and he has done a lot of testing with a lot of materials
When you make the mould, it’s enough that the real stone is wet from water. No need to use any soap or Vaseline. Soap is anyway more dangerous than petroleum spirit. Petroleum spirit leaves the mould and casting with time, but soap you must wash and wash and there maybe is still some soap left in casting.
Soap is very dangerous to micro organisms and bacteria, for example nitrobacteria sp., nitrospira sp. etc.
I don’t know if Sune has tested any types of vegetable oil, for example olive oil, for a mold release. I think that it might work and it’s quite safe too.
It’s coming very sunny and beautiful weekend. We still have over 50 cm snow here and nights are under 0 degrees Celsius. Spring winter in here Lapland is best time of year - so afternoon to Ylläs and some skiing and enjoying the beautiful sunny winter weekend!
Waiting for test results...
Model Railroader article uses same technique as Jyrki for making the Latex mold: http://www.trains.com/mrr/default.aspx?c=a&id=381
Model Railroader article that uses latex and RTV silicone to make the mold. It specifies Woodland Scenics: http://www.trains.com/mrr/objects/pdf/m ... ing_01.pdf
Woodland Scenics makes scenery supplies for the Model Railroad hobby. When you go to the home page, go to “Terrain” in the list on the left. Select “Terrain Accessories” for their Latex Rubber to make the rock molds-Product # C1204. Back to “Terrain” and select “Rock Molds” to see a selection of pre-made rubber molds in various sizes up to 10.5”x5”. They make paints for the rock castings, but they are used on railroad layouts in air. I don’t know if any would be suitable.
I ordered a Woodland Scenics rock mold from a hobby shop today. It should be there by Wednesday. I want to try a mold.)
I bought the number C1242 Washed Rock mold. It cost $8.79. These molds are flat and would only be suitable for use on the bottom of the tank as a foundation with other rocks placed on top. They are made out of Plastisol, I don’t know which type, but here is a link to the first site I found: http://www.qcminds.com/plast.dipcoating.htm
I am thinking it might be possible to glue other molds together with the mold to make it larger. It wouldn’t have to match exactly. I don’t think I will pursue it for now though.)
In chapter 4 of “How to Build Realistic Model Railroad Scenery” by Dave Frary, published by Kalmbach Books, ISBN # 0-89024-124-4, the author covers in great detail how to make latex rubber molds of rocks.
He adds a step after washing the rock where he brushes on a detergent solution (6 drops/qt. water) prior to applying the first coat of latex. This is to allow the latex to get into the cracks easier and act as a mold release.
I read this chapter over and highly recommend anyone getting a copy at your local hobby shop or by inter library loan. The chapter goes into a lot of detail in the mold making process.)
In chapter 10, Workshop Hints, in “303 Tips for Detailing Model Railroad Scenery and Structures” by Dave Frary and Bob Hayden, published by Kalmbach Books, ISBN # 0-89024-243-7, the authors touch on casting using Alumilite, a buff colored plastic casting resin.
I went to the web site and find they have a large selection of mold making supplies and casting resins, colors, etc. Looks like a gold mine!
I tried US Gypsum to see if they had any products suitable for this project. They don't but the person I dealt with gave me two links, the first one is for a company in Michigan called, The Nature Factory. They make displays for high end homes, amusement parks, aquariums etc. The link: http://www.thenaturefactory.com/index.htm
I thought some of you might be interested in this company.
The other link is for company that specializes in molding of many types, including Glass Fiber Reinforced Concrete (GFRC) products. Basically, this is the addition of a layer of fiberglass cloth between the layers of the SikaTop Seal 107. (3/16/07 The previous statement is incorrect. GFRC is the addition of short glass fibers to the concrete or mortar mix. Also, the mortar product won’t stick to fiberglass cloth. I will touch on the use of fiberglass cloth in the section for the “Aquarium lacquer" NM Klarlack FS 023/80) I suspect if this were done it would eliminate the need for the Sikagard 62. The addition of the Sikagard 62 layer is for added strength. The fiberglass would do that as well. The link: http://www.ball-consulting-ltd.com/
This company offers mold making rubber products, mold releases, pigments. They sell through a company called Arizona Sculpture. http://www.arizonasculpture.com/
I forgot that the US Gypsum source provided me with a link to a company called Smooth-On that makes liquid rubbers and plastics. Their site is loaded with detailed directions for making molds, using sealers on the item to be molded: (I saw Vaseline thinned with Mineral Spirits listed as a sealer!), mold releases, hints, etc. The link: http://www.smooth-on.com/
Overview of casting using concrete as the casting medium:
http://www.smooth-on.com/PDF/Concrete%2 ... ntials.pdf
Using urethane rubber as the mold for concrete castings, it also mentions a water based mold release for use in the mold when making the castings:
Evaluate latex rubber and urethane rubber to see which is better suited as a molding rubber for our project. This is where the Smooth-on and Alumilite links will come in.)
I called Alumilite today and spoke to a representative of theirs. They sell mostly silicone rubber for mold rubbers. They have one urethane rubber. At the Smooth On site there is a “How To” section that compares four types of casting rubbers. When I compared the differences between silicone rubber and latex rubber, latex comes out best for our purposes, IMHO, and in agreement with Jyrki in his reply below; because it is cheaper, we don’t care that it will take days to make the mold, and we don’t want to make many multiple copies of the same rock on a commercial scale. Smooth On “How To” Moldmaking Materials: http://www.smoothon.com/howto1.htm
A link to Smooth On “How to Make Molds and Castings” http://www.smoothon.com/howtomakemolds.htm
Here are some sources for latex rubber to make the molds. There is another source for pre-made latex molds of rocks suitable for Model Railroading but great for us too. Some very large molds there.
Sources for latex rubber:
(3/16/07 http://www.artmolds.com/product_details ... x%20Rubber
ArtMolds Sculpture Studio
18 Bank Street
Summit, NJ 07901
(TOLL FREE) 1 866-ARTMOLDS (1 866-278-6653)
(3/16/07 http://www.tapplastics.com/uploads/prod ... n%207A.pdf
(8-6:00 PST, M-F)
TAP Plastics Inc.
1859 Pacific Avenue,
Stockton, CA 95204
Latex page of Bare Metal Foil Company. Has mold making supplies. Home page: http://www.bare-metal.com/index.html
Castcraft • PO Box 17000 • Memphis • TN • 38187-1000 || Home page: http://www.castcraft.com/index.htm
http://www.delviesplastics.com/Merchant ... ing_rubber
Delvie's Plastics Inc.
133 West Haven Ave
Salt Lake City, UT 84115
Fax (801) 467-1540
Pre made latex rubber rock molds for Model Railroading. Catalog shows pictures of the rocks molded. Home page: http://www.bragdonent.com/index.htm
2960 Garden Tower Ln.
Georgetown Ca 95634
Don’t forget the Woodland Scenics source for latex rubber. The links are above.)
*****"SikaTop Seal 107 special plaster"- A cement based product. It needs a leaching process prior to use in the aquarium to avoid raising GH and conductivity as he says in the sidebar on page 31. It remains slightly "elastic" - flexible, after curing as he says on page 29 in the text.
http://www.sikaconstruction.com/tds-cpd ... 107-us.pdf
http://www.sikaconstruction.com/sc-cpd- ... 107-us.pdf
http://www.sikaconstruction.com/msdsa-c ... 107-us.pdf
http://www.sikaconstruction.com/msdsb-c ... 107-us.PDF
I saw some Sika products in a Home Depot today. None of the SikaTop Seal 107. They did have a Sika latex admixture for cement. I wonder if it is the same as is included in the 107 product. I will find a local distributor and get some.)
I called my local Sika distributor and got prices for the SikaTop Seal 107. In Northern New Jersey it is $46.00 for a 44 lb. unit made up of the liquid Acrylic latex admixture called part A, and 35.5 lbs of a special mortar mix called part B. They are mixed in a 1 part by weight part A to 4.5 parts by weight part B ratio for a trowelable mix. This is enough to make 2.65 gallons. I don’t know how many castings it would make. Once the liquid is opened it has a 6 month shelf life, so make all of your castings as soon as possible.
I tried to buy a product called SikaLatex ( http://www.sikaconstruction.com/tds-cpd ... tex-us.pdf
) which is very similar if not identical to the part A of the Top Seal 107. It is only sold in cases of 4 one gallon containers at around $23.00 per gallon. Out of my price range. When talking to Sika customer service I asked about the Home Depot product I saw the other day. I was told it is called SikaLatex R ( http://www.sikaconstruction.com/tds-cpd ... exR-us.pdf
). This is a diluted latex admixture. It may be a 50% dilution. I say that because in reading the data sheet for SikaLatex in the section, Mixing Procedure, it says to dilute it 1:1 with water when using it as a primer. The tech sheet for SikaLatex R in the same section says to use it at full strength, no dilution is necessary. Both of these products are used in place of water when mixing mortar mix up. It would even be possible to use 1 part Portland Cement, 2 parts of your own substrate to match the casting to your substrate, and the latex admixture so you still have the 1 part liquid:4.5 part dry mix ratio. The colors need to be added when mixing the dry ingredients together before mixing in the liquid.
Here is a link to a Sika “How To” page for SikaLatex R and other products: http://www.sikaconstruction.com/ht-cpd- ... exR-us.pdf
The MSDS is the same as the SikaTop Seal 107 Part A and the SikaLatex.
What I am going to do is to buy the SikaLatex R at Home Depot and mix it with a latex rubber molding compound to try and bring it back up closer to the strength of the SikaLatex.
I could also try to evaporate it until it is reduced by half in volume. I remember reading in one of the links about the latex rubber containing ammonia while liquid as a preservative I believe. I can’t remember just now where though. This source said that if the molding rubber got dried out it could be reconstituted by adding distilled water with a little concentrated ammonium hydroxide, not household ammonia. Add enough to give it an ammonia odor. The Sika product does have an ammonia odor according to the MSDS sheet. Evaporation will remove the ammonia too. Something else to think about.)
I did some Internet searching and found out that the “latex” of latex rubber is different from the “latex” of the Sika products. My idea of fortifying the Home Depot SikaLatex R with the latex rubber molding materials would most likely fail. I am not going to try it. I am also not going to evaporate the product.
Latex rubber is a natural product obtained from rubber trees originally found in South America. 0.6 to 1.0% Ammonia is added to the latex obtained from the trees after it has been strained to remove dirt and debris within 3-4 hours to preserve the strained latex. It contains around 40% solids. It dries to a thin clear coating and is a milky looking fluid. The latex of the Sika product is an artificial product. It is Acrylic latex. It was right there in the MSDS sheets but I didn’t know enough to recognize the difference. These products: Acrylic latex, Polyvinyl acetate latex, and others are what are found in “latex paints”. They dry to clear coatings and are milky when liquid, hence the same name. I found this information in this link:
Here is a link explaining the manufacture of rubber bands which includes a discussion on natural latex. http://www.madehow.com/Volume-1/Rubber-Band.html
I am grateful to Stuart Halliday in his post to the Aquatic Plants Digest , Vol 43, Issue 18 on March 27, 2007. The thread is: Re: Attaching Java Moss to bogwood. The link is: http://fins.actwin.com/aquatic-plants/m ... 00044.html
I see from Jyrki’s response below that he gets about 12 man head sized castings out of each unit of SikaTop Seal 107 with some left over. This works out to about $3.00 to $4.00 for each casting. This is cheap, considering the cost of Lace rock. Thanks Jyrki, for your input. This helps me. I think I am making more work for myself by trying to find alternate products now that I know the yield. I would caution anyone trying other cement admixtures by other manufacturers. I saw one that contained an antimold and antifungal product. I would think it would be dangerous to our fish or plants.)
I checked the price of the SikaLatex R at Home Depot last night. It is about $11.00 per gallon. Since it appears to be a 50% dilution of SikaLatex and the Part A of SikaTop Seal 107, it isn’t significantly cheaper.
Jyrki responded to my estimation of the yield from a unit of the SikaTop Seal 107 the following:
“Quote: "I see from Jyrki’s response below that he gets about 12 man head sized castings out of each unit of SikaTop Seal 107 with some left over."
Almost twenty (20), maybe over, I haven’t counted them exactly. If you have friends who are interested to use SikaTop seal, its good idea to buy it together and make it half. Half unit is still lot of material.”
This is a greater yield than I estimated, and so even better!
The sample of the casting Jyrki sent me is much thinner than I thought it would be. I estimated it would be ¼ to 3/8 inch thick. I was way off. It is less than 1/8 inch thick (about 3 mm). The coating of epoxy is around 1/64 inch thick (0.4 mm) or less.
I ordered 1 unit of the SikaTop Seal 107 today. I am waiting to get the pickup authorization before I can pick it up.)
Investigate whether another casting substance would work just as well as Jyrki's SikaTop Seal 107 with pigments added without the fears of metals. This is where I will look at the Alumilite site and any others that come up.)
In the call to Alumilite I discussed using urethane as a casting material. When you follow the link in Jyrki’s post below “(Who is Sune Holm?)” you will find a fascinating site for the Back To Nature background manufacturing company. Sune Holm was one of the founders of the company. They use a urethane resin to cast their backgrounds.
Alumilite doesn’t sell urethane as a food safe product due to the “Human Factor” when mixing the urethane resin. If not made in the proper proportions, or cured properly, unreacted chemicals will remain in the casting. These contain isocyanates. These products can release cyanide if acidified. That is the liability concern. If the two parts are carefully weighed to give a 1:1 by weight mix, then the chances of having isocyanates are greatly reduced. There are other factors involved which if you call Smooth On yourself, you can ask about.
A urethane casting can be painted. I started a project a year or so ago where I was going to try and paint plastic rocks I purchased to make them look more realistic. Krylon makes paint called, Fusion, which is made for painting on plastics. I don’t have it here so I can’t read the label to see if it works on urethane, but it works on most plastics. I posted on this Forum about this project last year. Here is the link: viewtopic.php?t=198
I never did finish the project. Now that this section of the rock has been in the tank for over a year, unpainted and just as I purchased it, it doesn’t look too bad. Not as good a Jyrki’s castings by a long shot though.)
*****""Aquarium lacquer" NM Klarlack FS 023/80"--I wrote to Jyrki and he gave me a link in Finnish to the manufacturer: http://www.epotex.se/page/139/154/26/54
Jyrki said to use any two part epoxy paint which is food safe, toxic free, or drinking water approved. He said he only painted the inside surfaces of the casting to make the stone harder. He also said not to paint the outside as SikaTop Seal is drinking water safe and the outside will look more natural when it is not painted with the epoxy paint.
I called Sika today and they have a food safe two part epoxy that is very similar to Jyrki's "lacquer" product. It is called Sikagard 62. Links:
http://www.sikaconstruction.com/tds-cpd ... d62-us.pdf
http://www.sikaconstruction.com/msdsa-c ... d62-us.PDF
http://www.sikaconstruction.com/msdsb-c ... d62-us.PDF
Read the Technical Data Sheet for directions. It will say not to apply to cement until 21-28 days have passed from first mixing. This really doesn't apply in this application as we are not concerned with a waterproof application. As the cement cures it gives off water. If it is fully covered by the Sikagard 62, the water will escape and cause pinholes. This application only covers one side. No problem for us. Pinholes don't matter either.)
I called the Sika distributor today and got the prices for the Sikagard 62. The smallest unit is 1 qt. (1 pt. Part A and 1 pt. Part B) It costs $45.00! This is way out of my price range. I called a paint store and they do have an epoxy product good for use on concrete that was around $12 for a pint. Fiberglass cloth can be embedded in the epoxy to give more strength to the rock casting. This should be available in HD or Lowes. Auto parts stores will carry it too as it is used in repairing cars too. Check your local surf shop if you have any around!)
The paint store had two epoxy products; one is a porcelain refinisher product to fix sinks, the other is a putty compound. I didn’t want either.
I tried to find sources for fiberglass resin on the Internet and discovered there are at least two types: Polyester and Vinyl Ester. Both absorb water over time and may detach from the cement casting. This is according to Tech service at U.S. Composites in Florida, http://www.uscomposites.com/
He recommended I try their two part epoxy called 150 Thick with the 1:1 hardener The cost is $9.50 for 1 pint, $13.95 for 1 Qt. http://www.uscomposites.com/epoxy.html
Some other epoxy resins I looked at cost in the range of $100. per gallon or more. The tech salesman said we could try adding chopped glass fibers to add strength to the epoxy. Click on the link to “powder fillers” Also, the batch can be mixed in small quantities as long as you are really careful to get a 1:1 by volume mix. When mixing it will be very thick and will need stirring for at least 5 minutes before using. Complete mixing is essential.)
I ordered 1 Qt. of the 150 Thick with 1:1 hardener today. Coming UPS Ground.)
*****”Earth color powder dye” Jyrki used the company, Uula-tuote in Finland for his pigments. The link to the English page on raw materials: http://www.uula.fi/englanti/pigments.htm
) I have emailed and asked whether their iron oxide pigments contain metals other than the iron oxide.
No answer to the email to Uula-tuote about the metals yet. Now that I have Jyrki’s samples of the pigments, I am not going to pursue a response.)
I asked technical service at Sika about coloring the SikaTop Seal 107. He said we can find colors in any hardware store. Cement is frequently colored. He mentioned Davis Color, Sakrete, and Quikrete as possible manufacturers for pigments. I haven't checked them out yet.
I have a few links but still haven't checked all for their suitability in our tanks. I only skimmed the following sites. They look great. I don't know yet if they have any food contact colors, i.e. non-leaching.
Davis Color http://www.daviscolors.com/literature/pdf/conColor2.pdf
Butterfield Color http://www.butterfieldcolor.com/color_chart_index.html
Lambert Corporation http://www.lambertusa.com/color/
I contacted Davis Color today. Here is the correspondence so far.
Ferric Oxide would be fine in an aquarium. I use Ferrous Sulfate weekly to add iron for the plants. Others use chelated Iron. If any leached it would be a nutrient. Are you saying all of your pigments are Iron Oxide based?
What do you mean by, "If our pigment was placed on the top a good portion of it would be carried away......"? What do you mean by carried away?
I will check color hardeners, to learn what they are.
Let me give you some more information about what we are trying to do:
Prior to molding, the mold is coated with a thinned mixture of 6 parts thinner and 4 parts Vaseline. The solvent is allowed to evaporate. This will become a mold release. Then black pigment is wiped on the high points on the surface of the mold to darken the recesses in the rock casting, while leaving the high points the base color.
The author uses Earth color powder dye (brown, terra-cotta, or any other shades preferred) sold by Uula-tuote in Finland, which are mixed into the SikaTop Seal 107. This would produce a more even color throughout the casting, as it is mixed into the cement.
The front surface of the casting, tinted with the black in the recesses will not be sealed. It will be left unsealed as it will look more like a rock that way. The back surface of the casting will be coated/sealed with Sikagard 62, a two part epoxy mix. This is added solely for extra strength for the casting. The finished casting will only be about 1/4 - 3/8 inch thick. We are trying to simulate large rocks without the weight and without the volume. Real rocks displace too much water from the aquarium. The hollow back will also provide caves for the fish to hide in. Picture bowls with the outside being the visible side in the aquarium, and the inside being the epoxy coated side.
Thanks for your help so far.
>From: "Miner, Eric" <E.Miner@RPigments.com>
>Subject: RE: Web Questions/Comments
>Date: Fri, 2 Mar 2007 14:06:57 -0500
>I'm not sure what the Finnish used. We have Iron Oxide color pigments that are pure Fe2O3. These pigments are meant to be used integrally in concrete. They may be using what we call a color hardener that is used on top of concrete; it is made for this purpose. If our pigment was placed on the top a good portion of it would be carried away or blended into the sealer used.
they would have the color hardeners.
>Sent: Friday, March 02, 2007 9:14 AM
>To: Miner, Eric
>Cc: Fox, Robert
>Subject: Web Questions/Comments
>ProjectTypeOther: hollow backed castings
>Message: I am a tropical fish hobbyist. You could call me a fanatic. I read an article in The Aquatic Gardener covering the use of SikaTop Seal 107 in latex rubber molds of rocks to create large hollow rocks. The author is Finnish and I am collecting US equivalents of the products he used. He used dry pigments to sprinkle on the rubber mold prior to filling with the SikaTop Seal 107.
>My question is: What are the pigments made out of? I ask this question as the castings will be kept in an aquarium with fish and aquatic plants. Will they leach into the water? We fertilize our plants with trace elements.
>Are the pigments metallic salt based? I don't need to know the specific compound, as in copper sulfate, just copper would be sufficient.
>Jerry Smith )
No answer yet to the letter to Davis Color. The black pigment many offer is Lampblack. Here is one link to a site selling pigments. http://www.naturalpigments.com/detail.a ... ID=480-50S
There was some mention of not using lampblack in wet areas. I haven't followed up on this yet. There are iron based black pigments. These may be more suitable for us. )
I spoke to Davis Color today and confirmed that Lampblack is not suitable for long term color fastness. He said that he hasn't heard of any installation of outdoor concrete using lampblack that maintained its color for more than 5 years even though it was sealed. Iron based black is for us. The price for 1 lb. of pigment in the red, yellow, black range of colors is about $7.00. That is a lot of pigment and should be plenty. Blue and greens are much more expensive: $70.00 per lb. or so. The blue is cobalt based. Not sure what the green is. The other iron based pigments can be blended to get what ever shade is desired.)
I read the MSDS for some of the earth colored iron based pigments yesterday. In section 15 Regulatory Information various metals are listed and the maximum concentrations. Copper is there with a max concentration of 800 ppm. This raised a red flag for leaching into the aquarium and killing any invertebrates present. As I thought about it, I remembered that the EPA views the incineration of various fuel bearing hazardous wastes in cement kilns as a safe practice as the metals present will become stabilized and solidified in the cement formed. The concrete pigments act as similar additions to the cement. The hardened cement locks up the pigment.
Now, I do want to know what happens to the metals, because if they do leach out into our tanks we will have problems. I called a hazardous waste treatment facility I use in my work. They regularly treat hazardous wastes by mixing with cement to make concrete which is then landfilled. The concrete they make needs to be tested by a test which simulates leaching by acid rain called Synthetic Precipitation Leaching Procedure (SPLP). Or disposal in a landfill called the Toxicity Characteristic Leaching Procedure (TCLP) test. The waste is mixed with an acetate buffer at pH 4.95 for a certain period of days and then the liquid is tested for the presence of metals within certain allowable limits. In the case of the concrete, the procedure works and meets the limits allowed by the EPA. )
I called the Portland Cement Association and spoke to a technical service person and asked questions. He says due to the many variables in the curing, mixing, temperatures, humidity, etc. of concrete it is hard to get specific values for specific metals leached from concrete. He was able to give me some values for metals in the dry cement prior to mixing into concrete. He followed by stating that most if not all fish hatcheries in the US use concrete for the fish pens without problems. I visited the NY Aquarium a few years ago and had a behind the scenes tour. Their tanks are concrete too.
I called the PCA again to see if I could get any written information on the metal content of dry Portland cement. As I spoke to the representative I was told there are only trace metals in the cement. No values were published. He also said that the chemistry of cement hydrating is not fully understood and occupies entire textbooks. The layman's explanation is that as water is added to cement, crystals grow between the cement particles which chemically prevent the metals the cement contains from leaching out. I was really looking for some published reports, but none to be had there, at least for free. There is a $25 CD which contains a report numbered EB071 that may pertain, but I am not going to buy it.)
Contact NJ Pequest Trout Hatchery to talk to staff concerning their research or knowledge of metals in concrete. Link to their new water monitoring system: http://www.nj.gov/dep/fgw/artpeqmonitor07.htm
Called Pequest and was passed around to various departments and labs until I spoke with the supervisor. He was there when the facility was built. He is checking the records for me to see if anything was done regarding the curing of the cement. The overall reaction of all I spoke with was they weren't aware of metal content in cement and that I am talking about a research project. They were all very interested, but had never come across this question before. The total flow in the hatchery is about 7,000 gallons per minute. If there is any leaching of metals which occurs, it doesn't affect the fish due to the rapid turnover of the water.)
Portland Cement Association link: http://www.cement.org/
The recommendation I received was to make sure the concrete used is cured well. Here is his recommendation: Using the SikaTop Seal 107 as Jyrki recommends, cover the first layer with plastic wrap to keep in the moisture. Wait 12-24 hours and add the second layer. (Make sure to remove the plastic wrap first.) Let it solidify covered with more plastic wrap until it is hard to the touch, again 12-24 hrs. At this point, submerge the casting in an approx. 1 molar solution of Masonry Hydrated Lime for 28 more days. Hydrated Lime Ca(OH)2 is 74.1 gm/mole. To account for impurity use about 80 grams dissolved in water to make 1 liter. This is the 1 molar solution. Make as much as needed. The purpose is to provide a source of calcium ions to the curing cement.
After the 28 day cure, dry the casting and apply the Sikagard 62.
Next perform a 28 day leach of the casting with water circulation and water changes daily. At this point the casting should have a non porous cure and have maximum impermeability to water. This minimizes leaching of metals.
This is a pretty time consuming process. It is more than Jyrki did. Could it be anti liability based?
I searched the net for technical papers and did find some papers which showed the concrete passing TCLP. Most came from the Portland Cement Association website, but are links to EPA papers. I also called someone I know at the EPA's Region 2 office. So far he hasn't returned my call. I expect he will though.
Email and phone call have been placed to the EPA Region 2 for insight into concrete as a suitable stabilizer of metals within the rock casting. Waiting for responses.)
My EPA contact was out of the office for a few days and called me today. He will check my email and try to get back to me by next week. Very kind of him.
The response to my letter came from my contact in the EPA today. I am deliberately not using the name of the source. This is the letter I sent on March 8, 2007:
“I am hoping you can direct my question to an appropriate person.
I am wondering how and to what extent concrete stabilizes metals. I am working on a project for an aquarium I maintain here at work based on an article written by a Finnish aquarist and published in the most recent The Aquatic Gardener. The author made rubber molds of large rocks and made castings of them with a concrete product. They are used in an aquarium to lighten the load of real rocks on the bottom pane of glass.
I am searching for US equivalents to his Finnish products. I am documenting my search for the benefit of the members of The Aquatic Gardeners Association at: http://forum.aquaticgardeners.org/viewtopic.php?t=754
The concrete itself contains metals as I found out from the Portland Cement Association. The iron based pigments sold by Davis Color contain up to 800ppm copper according to the MSDS. Copper will kill the invertebrates many aquatic gardeners keep in their aquariums if it leaches into the tank. I know concrete is used in Stabilization and Solidification of hazardous wastes. Do you know if the copper can be expected to leach from properly cured concrete, with a leach period after the cure and prior to use in an aquarium?
This is the response I received today, March 20, 2007:
Sorry it took so long to get back to you. I have spoken to several people here and no one has a definite answer. The consensus is that it 'should' be OK but no one is absolutely certain that no leaching will occur. I presume that you contacted the manufacturer?”
Back to my comments: So, both the Portland Cement Association and the EPA cannot state for certain that no leaching will occur. Jyrki’s fish survive, others using cement have their fish survive, maybe I am worried about nothing.)
A link with information on stabilization and solidification: http://www.concretethinker.com/Papers.aspx?DocId=19
I want to see if I can get some of my contacts to do some metals testing for me "for the good of the hobby". More later. )
Jyrki mentioned at the end of his post that he is going to send me some materials for testing. I am glad he is going to do this. I asked him to send me an old small rock casting plus some of his raw materials. I would like to leach his casting in distilled water for two weeks and test the water for metals. I want to test the raw materials as well. I plan to use the mold I am purchasing to duplicate Jyrki’s steps exactly and use the casting I make to test in the same way, except I won’t soak in distilled water until the casting is leached like Jyrki did. I plan to test the raw materials I purchase for metals as well.
Now that Jyrki has agreed to send me the materials, I will start the other half of this project: talking to my contacts to see if they will do the testing, “for the good of the hobby”.)
I called the person I was thinking about today for the metals testing. He is happy to help. Thanks JR. Once Jyrki’s samples arrive I will be able to start. It is going to take about 3 weeks before all the leaching is complete. The samples will be preserved with Nitric acid to <pH 2.0 until I have them all. No need to send samples over the course of time. Once preserved they are stable for 6 months.)
Jyrki’s package arrived today safe and intact. He sent: Three samples of the pigments, Brown umber, Natural Terra, Black Oxide; a sample of each part of the SikaTop Seal 107; and a 1 ½ yr old broken off piece of his rock casting that has some dried moss still on it. It must have come fresh from his tank and been leaching all this time. Thanks Jyrki.)
I emailed Jyrki: “Your materials arrived today in excellent shape. Thank you very much for sending them. I will get to the testing as soon as I can get my own raw materials. I will be speaking to my friend this coming Saturday PM. We have a dinner for our society and Jr. is planning to be there. I will find out how he wants to do the testing, in a series of tests spread out over days; or all at once. I hope he can test the dry materials you sent as soon as possible.”
I bought Sakrete Charcoal and Buff pigments at Home Depot last night. I didn’t like the red. It was too red. A 1 lb. package cost $5.49. This is a lot of pigment.)
*****The Experiment in Metals Testing:
Before I begin the testing there is one thing that I must mention. Since there are so many cement kilns around the country, if I find metals in one brand of cement it won’t mean that all cements have those same metals. We must be careful how we understand the results of the testing on the dry materials.
Last Monday I spoke to someone at a company that mixes treated hazardous waste with cement to solidify it. He also happens to be a pond hobbyist. He doubts I will see any metals. He explained that the cement forms a Calcium silicate crystal which binds up the metals. He said that I should even crush the molded stone prior to leaching and even then he doubts any metals will be found.
He gave me some hints in order to get reasonable results:
1. He said to try to keep the same proportion of molded rocks to the volume of water which will be found in the aquarium. Otherwise any metals will be too diluted and it won’t be a representative test.
2. He reminded me that the MSDS values for the metals in the pigments are for the pure pigment. He pointed out we aren’t putting pure pigment into the tank, but pigment mixed with cement. It is diluted. The box of pigment says to mix 1 lb of pigment with 80 lbs of dry mortar mix. The water added to it is about 16.5 lbs to keep the 1 part by weight liquid: 4.8 parts by weight dry ratio. This is a total of 96.5 lbs of mixed up mortar containing 1 lb. pigment. I will call that 1/100. So for the 800 ppm copper max in the pigment, there will be 8 ppm copper in the mixed up mortar. This is something I should have thought of before.
This is a really big difference. If I keep this pigment ratio in the SikaTop Seal 107, there will most likely be no problems with metals. I will still test them to be sure though.
The SikaTop Seal 107 arrived today. The epoxy still hasn’t arrived. I will send out samples of the dry materials tomorrow.)
I have been very tied up at work and didn’t get the samples sent out until this afternoon. I sent all of the pigments Jyrki sent me plus the two I bought, plus a piece of his casting he sent me. I started leaching another piece of it today in distilled water. I sent the mortar portion of the SikaTop Seal 107 only. The acrylic latex portion is a product I wouldn’t expect to contain any metals, so I didn’t send it for testing. I am not testing for organics leaching out, just metals.
I was speaking to the owner of the testing lab I use and he is willing to do the testing gratis for me. So, I spoke to his lab manager today and determined to do two tests on the raw materials.
The first test will be a modified TCLP test on the raw materials. I estimate that Jyrki used 22 lbs of material to make his rock castings. This is probably high, but it is a starting point. They are in a 140 gallon tank (1166 lbs. water). This is the ratio of leaching liquid to dry material we will use. An acetate buffer at around pH 5.0 is the leaching liquid. The real test goes for about 18 hours and is supposed to simulate one month’s leaching in acid rain. We are going to leach for twice as long.
The pigments are mixed into the castings at a 1% concentration. We need to take this into account.
The second test is replacing the acetate buffer with Lake Tanganyika water made up with Seachem Cichlid Lake Salt at 11 grams per 40 liters and Seachem Tanganyika Buffer to a pH of 7.8-8.2 in distilled water. This one will leach for two weeks to simulate the time period between water changes for a lazy hobbyist like me.
This lab will then digest the leaching waters with the conventional sample preparation for testing on an ICP- Inductively Coupled Plasma instrument. This will simultaneously check for 23 metals. This is a lot better than the AA I was planning on using. There you can only check for one metal at a time. Each metal change requires an entirely new calibration setup.
I have not made any castings yet. I will not be able to do so this weekend either due to further work pressures. When I do I will have them tested as well.
More to come!)
I leached Jyrki's rock casting for 22 days in distilled water. I have preserved a sample of the water with HNO3 and will send it to the lab. The lab has not started any work so far on the samples I have sent. I spoke to the technician that will be doing the work. He now has a good idea of what I want. His supervisor has been on vacation and he wasn't sure what exactly needed to be done.)