DIYbanter - View Single Post - Non-toxic materials

wrote:
I've found some literature that says shellac sealing properties vary
based on age and at the best of times it's not a 100% barrier at all.
But still better than nothing.

The best shellac is mixed fresh (meaning within a few days) before use.

I'm in the process of ordering activated carbon for my ventilation
system, which I'm building with overkill in mind.

Remember that downflow is better than up or sidways flow as the
flow then keeps the particles tightly packed. Activated carbon can
be desorbed for reuse by blowing hot clean air through it, if
expense is an issue. Be careful you don't set it on fire though.

I use acrylic paint, also work with plaster, latex, gelatin, various
stones, watercolors. I don't think artist's acrylics are a good sealer
though and pretty expensive for furniture.

What is the solvent used in acrylic paint? MinWax Polycrylic
is a water-based claer wood finish. Those used to use some
petroleum distillates (I think ethers) and/or glycols and may
off-gas acetic acid or some such. as they cure.

I'm wondering about the toxicity of PVA glue... they say children's
glue is non-toxic... is it not really? Why not just thin it down and
apply it heavily over everything?

Well I suppose it is not very hard and not very water-resistant.
Shellac may turn milky when exposed to water (some say that
dewaxed shellac does not) but water doesn't otherwise damage
it. Wax is great for adding gloss to wood either directly onto
smooth bare wood or over a finish but it is a very poor vapor
barrier.

The methanol in the shellac should pretty much all flash off or
outgas pretty quickly I would think. Small traces of methanol
are found in wine and liquors and even canned tomato jouce.
If you can tolerate those, shellac made with denatured alcohol
may not be a problem. But do check the label, many manufacturers
use other denaturants. At one time sulphuric acid was used but
probably discontinued as it was too easy to 'renature' it by
neutralizing the acid.

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FF