Maybe something like General Finishes Salad Bowl Finish or Mahoney's Food Safe Fine Finish. Some people can have an allergic reaction to some exotic woods.
Rockler - Search Results for 'finish'
Hi Joshua and James:
I've just taken a look at the General Finishes Salad Bowl Finish data sheet.
http://www.generalfinishes.com/sites/default/files/MSDS-GF-Salad-Toy-Makers-Clear-2-4-09.pdf
There are short term and long term warnings on this product.
I'm going to be the devil's advocate here and examine this from another side.
The person who told you "trade secret" is probably using a product that wasn't intended for close skin contact use and doesn't want to get caught. My wife buys something and tries it on for a few days. If it causes her a problem, it gets dumped into the bottom of the jewelery box and I chalk another one up to "poor product." She never takes it back to the vendor for her money back.
In the jewelery world, manufacturers have been hiding behind "trade secret" for centuries. It has always been a "buyer beware" industry with no clear research being done or if so, I've not seen it documented. Our involvement with an outfit called "Fifth Avenue" bore that out clearly.
I would contact various finishing companies directly and see if any will stand behind their products in close skin or broken skin environments. The broken skin is the killer.
I would also look at the various plastic coatings that are available. Some of them will produce a hard non-leeching surface that might be suitable for your environment. Most manufacturers make them.
You might also test various natural oils like olive oil, palm oil, coconut oil, and preparations like french polish. French polish is boiled linseed oil (listed as "slightly hazardous in case of skin contact [irritant, permeator)", alcohol and shellac. Given the natural sources, it is possible that it might be suitable. I've just looked at the MSDS of shellac. "prolonged contact may cause skin irritation" Zinsser & Co. However, their product is a spray application and the hazardous materials appear to be solvents and propellants for application with little to do with the shellac itself.
I've found an MSDS sheet on shellac gum. "Slightly hazardous in case of skin contact" I heard somewhere that shellac was one of the constituent parts of the polish on pills and other "candy coatings." Research this last statement carefully though. I'm not a biochemist.
I also thought of mineral oil, but the MSDS sheet is not nice.
If such a product exists, it shouldn't be difficult to find it. It may require persistence. We have a perfumer here that does a lot of research in skin environments. Check around your area and see if you can find one. He will certainly be aware of any such preparations and may be able to "create" one for you. You might also check with people in the world of essential oils and "natural" products. Even a naturopath may be useful.
I would also suggest that you find woods that are non toxic. I think poplar, pine, and (sugar) maple are non toxic. You can heat sand, insert a small piece of wood for a few seconds and it will be mildly burned on the surface and it will give you a beautiful shading effect that may be ideal for your world. For instructions, look into the marquetry world.
This is all I can think of for the moment. I'd be interested to hear of the results of your research and what you based your decisions on.
