Hi,
I'm planning on building a 3D rock background out of polystyrene to place inside my aquarium.  The plan is to sculpt and shape the polystyrene 'rocks', stick them individually onto a thin flat polystyrene backing sheet and then brush it with several epoxy resin coats (with suitable dyes if needed) to achieve the right colours and a bit of strength (the polystyrene itself is inert and does not need to be sealed off completely from the aquarium water).  I'm hoping to achieve a matt dark grey slate colour (or ideally shades thereof).

The polystyrene is then glued to the inside of the tank with silicone aquarium sealant.  The size of the 'wall of rocks' will be 7ft x 2 ft with depths of up 3 inches.

Researching on the web shows others have done this but I'm a novice in terms of resins and am not sure of the products available and sutable for this.  Looking at your products, I'm guessing if anything is suitable in terms of my planned process, it'll be the Epoxy Coating Resin?

Are any of your epoxies and dyes aquarium-safe (usually anything ok with potable water is fine)?

I'm hoping you can recommend resins, dyes and approx. amounts (I appreciate the latter will be a guesstimate! to the nearest pack size will do). Also I get the feeling the resin dries to a gloss finish - any techniques to reduce the gloss effect also appreciated.

Thanks in advance
 
Hiren.

When fully cured Epoxies like EC coating epoxy should be safe for use in an aquarium.

I have done "fake rocks" for model railways and plastic model "dioramas" using several materials as base, and using a mixture of Marine Epoxy (West Systems) and oven dried  "washed" sand as a filler. I have used mixed colouring additives to get a good colour.

The very fine sand mixed into the coating Epoxy makes the surface look a lot less glossy, and you can sprinkle the sand onto the surface when wet, to make it even more matte, this affects the colour though.

most of my "rocks" were painted afterwards with matte paint, to get them to look even more "real" .. You can probably do the same by mixing different shades of Epoxy resin and simply painting it on ... any shiny spots can be matted using steel wool ..

Good Luck!  

"Sapere Aude"... Dare to KNOW!

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103% of all people do not understand statistics...

Do not adjust our mind, theres a fault in reality :-)

To reduce the gloss you can just flat them down using sandpaper.

To calculate how much you need is a bit more difficult, although generally for a good coating we recommend about 1kg of Epoxy Coating Resin for each square meter of surface coverage.

In terms of using in water, you MUST ensure the part is fully cured before putting it into water. Uncured liquid epoxies are almost always toxic in one form or another. The Epoxy Coating Resin is dangerous for the aquatic environment uncured.  I recommend you leave it at least a couple of weeks to cure, preferably getting some warmth onto it to cook it off.

Also be aware that some pigments and dyes use lead and other heavy metals in them.  My recommendation is to ensure your last coat of resin is a plain undyed coat that way any dyes that could be hazardous to the fish are sealed in.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

I seem to remember that West Systems stated that their Epoxy is "aquatic -life safe" after a minimum of 1 month at room temperature.

They stated that their epoxy will remain safe up to 60 degrees Celcius, after the recommended 1 month post cure.

Since EC epoxies ar Bisp-A phenolic resins like the West Systems types, they should be the same for practical purposes.

Post curing at slightly elevated temps, maybe using an electric blanket, will of course shorten that period a lot. 

Btw .. Warren, I have actually managed to get a sample of West systems Resin cured perfectly using EC fast hardener ... and using the EC recomended mixing ratio, which incidentally is the same as the WS ratio ... (I had run out of normal WS fast hardener   ) 

"Sapere Aude"... Dare to KNOW!

The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind...

103% of all people do not understand statistics...

Do not adjust our mind, theres a fault in reality :-)

That doesnt surprise me if the chemical composition was the same base chemicals.  Would have been just a different blend of additives.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Thanks all for your replies and advice.

Just juggling between using the EC Epoxy (I've no experience with resins - but its has advanges like strength etc.) or a thin cement mortar (which I have a little experience of, it raises the PH of the water but it's not a problem with the fish I plan to keep).

Thanks again

Hiren