Hello, Haven't posted in years but was searching for something and came across this thread (hello Woeisme - we used to chat)

(see last part of post for "solutions")

My books long packed but am going to post this (excuse any typos)... The material on this is way beyond the scope of this forum. Background in pre vet/zoo sciences, and decades of work as sculpturess in materials and most salient ended up with chemical injury due to exposure to these very classes of materials - some more some less toxic.

I was paralyzed, internal bleeding, multi organ breakdown so on so forth and did research on the way "down" and was vegetative for many years. Only by my own research into alternative therapies can I now post here (ie am functional).

As an artist I exposed myself and was exposed (schools, colleges) to a great many materials (now most don't know this but there are brand names for most classes of these products - read OSHA booklets on chemical properties, toxicity, and brand names. One basically has to understand human anatomy and physiology, neurotoxicology and other related fields to understand what these chemicals do to our systems (I had just been admitted to NYU for Masters in allied Health Field).

By law, with a Doctor's letter one is supposed to be able to obtain a MSDS - many companies never complied (material safety data sheet). (many companies lie outright about the safety of their products btw, the EPA is not the best barometer). Most of these are not only toxic when not cured, but even after they are (although the harder the material the less it outgasses over time - all plastics continue to out gas over time) I studied plastics and resins for years (but books long ago packed). Resins are of a great variety, but acrylic is not the same at all as resins. (although there are acrylic resins) There are hundreds of different products and one must obtain the MSDS to know exactly what is being discussed.

Resins range from pressure/heat cured (hardest, strongest and industrial use mainly) to the over the counter two part (or even one part). Two part is harder and usually stronger then one part (the exothermic quality ie heat makes it so due to it's properties). Acrylic is from an entirely different class.

One has to get the chemistry of these products then look up each chemical and see what it does to the various systems. None, I repeat none are completely safe.

Smaller organisms are more vulnerable then larger (think canary in the cave.) That said, many toxicity affects (built up over time and exposure duration) do not show up as drastically in short lived creatures verses longer lived ones.

I would never allow a creature to digest any "inert" plastic or acrylic simply due to it's ability (will not be digested) to clog it's system btw. And that's the problem with the softer acrylic - it breaks down in water over time (when wet water is it's solvent, when dry achohol, but that said, all things even rock over time can be broken down by water, and it is soft enough in property for this to occur inside the aquarium - over time).

Remember as well - just because a product does not smell bad, does not mean it is not harmful.

The foams are also toxic and break down over time (pretty fast actually) I read of several diy aquarium projects later becoming messes. The softer the product the more breakdown and toxic. Two part epoxy is most definitely more durable but again depends on product ie industrial acrylic resin verses craft epoxy (hundreds of diff products as Woesime states read the label - then look up the properties. Also realize what the EPA and our gov allows, allows a certain number of deaths per types of exposures (it gets worse, but don't believe everything you read)

If one uses acrylic - esp a small part just MHO and suggestion, once dried, apply a thin layer or to of silicone.

That will solve that situation easily.

Same with the harder two part epoxy resin. A thin smear (invisible) will seal "cure or skin coat" and will prevent exposure of water to product.

When I used the two part putty I applied silicone then a layer of sand to further disguise, but for me this fit the project.

Note the part of the article that mentions "sensitizers"... most of these chemicals fall into one or both categories of synthesizers (put to sleep like I was) and or sensitizers (once a certain amount of exposure, later, after much cell damage is done, (can be one big exposure or many small ones over time) then you are sensitized - meaning life threatening reactions to smaller and smaller exposures (so small most would not notice).

Sorry to be so long winded. Like most, I didn't give many of these products much thought - until I had to! lol (well sorta)
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There is a great book:

Artist Beware, Updated and Revised: The Hazards in Working with All Art and Craft Materials and the Precautions Every Artist and Craftsperson Should Take (Paperback)
by Michael McCann PhD CIH (Author) "Vinyl chloride, asbestos, benzene, lead, cigarettes, and now art and craft materials?..." (more)

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Example:

Q: Is there a difference between polyester, acrylic and epoxy resins?

A: Acrylic resin (but not acrylic emulsion, which is the basis of acrylic paint) is a thermoplastic, which means it is one of a group of plastics which can be heated and manipulated repeatedly, whereas polyester resin and epoxy are thermosetting plastics, which use heat or a catalyst to solidfy into a solid mass that won't melt down.

Acrylic is mixed from acrylic polymer, a dry powder, a methyl methacrylate monomer, a thin liquid, and usually an organic peroxide hardener of some sort. If pieces of any size are contemplated, an autoclave or hydraulic press is necessary for reducing air-bubbles and counteracting the internal stresses created by the strongly exothermic reaction. The dust is toxic, as is the monomer and its vapors. And the organic peroxides are especially poisonous, some of them being explosive and others causing instant blindness if they get in ones eyes.

Polyester resin, a syrupy clear liquid, is mixed with a small but variable amount of a strong catalyst, which causes the curing mass to heat up (and to craze if you've added too much.) It is versatile stuff, being useful for coating, casting, and building up composites, usually in conjunction with fiberglass cloth.

It is not as hard or as clear as acrylic, having a somewhat yellowish tinge to it. And it- and especially the catalyst- is also highly toxic, and is persistantly evil-smelling as well.

Epoxy resin works similarly, doesn't smell as bad, but it -and the hardener that makes it set- is a sensitizer, meaning that you can get a nasty allergic reaction after repeated exposure. Some hardeners are not as bad as others in this respect. Epoxy won't set water-clear like acrylic, and doesn't resist sunlight (UV) degradation as well, but works better with high-tech cloths, like Kevlar and graphite.

Almost any dry pigment (with a few exceptions- test first on a small scale) can be used to color these resins, as well as various inert fillers which also add color; there are also special polyester dyes available. It can be made opaque or transparent- acrylic is used for casting "plexiglas" sheets, among other clear things.

Be very careful when using any of these materials: these are generally considered industrial rather than art supplies, and you are expected to know how to protect yourself from their harmful effects. If you don't have the proper facilities for dealing with them, consider using safer alternative systems.

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All that said - I've found some "safer" solutions, but as the original poster noted many are of a larger more expensive quantity (pond paint so on).

Again, use artist paints in tube (cheapest) and after dried (give it a few more days) thin smear of aquarium silicone.

Same for any expoxy.

Car model (hobby) enamel - small amounts sold and not expensive... again thin smear of silicone. Enamels, epoxies are more toxic but more durable then acrylic.

(I painted the back of many of my aquariums with fine acrylic artist paint - all I had, and was surprised when I was letting the tank soak in the tub that later the acrylic was water logged and was peeling off. Again the water is not a dried acrylic solvent but it can and will flake, peel so on. Can not will. I let it dry and patted it back down!)

I have used two part epoxy (plumbers "putty", which I am pretty sure is what is being sold online for marine coral projects) I used this to set rocks over hard plastic (amazing strength and dries fast). To be sure, I used a thin coat of silicone over it to seal it once it was hardened and a week of curing.

I've just used "bondo" to seal an expensive break in a gigantic acrylic globe (I never work with any of these but did in this case due to globe costing over 250 originally and unlike the exposures at work with no safety precautions, I took them, 3rd tier mask, flooded with outgoing fan so on)(an extremely toxic product and in the same field of floor strippers so on) (btw, many perfumes and colognes, fabric soaps and softeners are of the same petrolium based class, and hence the chemically injured being "allergic" to them.)

I am/was looking for a smaller amount of "safe" (relatively speaking) paint to coat this ugly pink color.

I tested the white plastic mesh (to allow for light to come in) and wasn't sure, and thought a neutral grey would maybe be ok?

I am planning a moss mesh wall and have several large moss wood pieces which will go infront, so If I do not find a smaller amount of "pond" paint (I may call and ask for a sample, lol) I will either let the moss hide most of the ugly... or use silicone and the mesh or both.

Here are some thoughts though.

One can always use paint then when dried and more (it takes as someone mentioned longer to cure) apply a thin layer of silicone. This will seal it and works to protect the "skin" of the cure, and stop any further out gassing regardless of how minuscule.

Here is a product I used long ago when making my huge interior water fountain (hypertufa) pond. It is fantastic!

They have a sample package. (see second link) and is what I may order to cover my ugly bondo and seal any toxicity. It is rubber based.

http://www.sanitred.com/WaterFountain.htm#

http://www.sanitred.com/pricelist.htm

Mini Sample Pack
$26.95
Contains enough PermaFlex to coat 7.5 sq (2 coats)
Contains enough LRB/TAV mixture to apply a 1" dia. bead 2Â long

1/2 Pint PermaFlex
1/2 Pint LRB (Liquid Rubber Base)
1/4 Pint TAV (Thickening Activator)
Instruction