I'm very committed to using food colouring to stain wood for children's toys. However, they tend to bleed their colour when wet baby mouths chew on them - not a nice quality in a toy.
This trial is based on make-baby-stuff.com's articles about non-toxic paint for baby toys where the only option I found viable was food colouring (because acrylic can flake off, milk paint requires specialized products that I don't have, and water colours are too light in colour for me).
Make-baby-stuff.com suggests several natural wood finish ideas that I experimented with here over the food colouring.
Spoiler's alert: Shellac Finish and Sealer wins.
Step 1: Beeswax Trial
This whole thing came about after completing my rainbow stacking toy for my nephew (see my instructable)
I had used Clapham's beeswax salad bowl wax to seal this toy.
It didn't work - see photo 2.
I went back to the drawing board and tried different food colouring combinations under the beeswax. I reviewed Amalkhan's instructable where they used rubbing alcohol. I also found online reviews suggesting mixing vinegar with the food colouring.
I tried all of these suggestions under the beeswax to no avail (not shown here). In the next step I'll show you my second set of trials with these different processes.
Step 2: Tung Oil/Citrus Solvent Trial
Out of all of the oils on the make-baby-stuff article, Tung oil is cited to seal "very well".
I decided to try just one oil (due to cost) - so went for the best review.
For the food colouring stain, I tried:
- No additive
- No additive, sanded after colour applied
- Vinegar added
- Vinegar added, sanded after colour applied
- Rubbing alcohol added
- Rubbing alcohol added, sanded after colour applied
Over all of these combinations of food colouring, I applied 1, then 2, then 3, then 4 coats of the tung oil/citrus solvent blend. You are meant to apply until the oil pools on the surface of the wood - and I went coats past that stage.
Although most of the sanded options stood up to the HAND TEST (does the colour rub off on my hand), none of them stood up to the CHEW TEST (does the colour rub off on my lips).
Conclusion: it doesn't matter if you add something to the food colouring, it is only the sealant that matters.
Step 3: Shellac Trial: the WINNER
The previous trial was disheartening, to say the least.
I decided to one-off it with the shellac trial, as it didn't seem to matter if the food colouring had additives or not. I also decided not to sand after applying the colouring as it significantly decreases the vibrancy.
To my surprize: The Shellac passed both the hand test and the chew test with only one coat.
Shellac wasn't my first choice as there might be a possibility of an allergy risk (here is the direct quote from the make-baby-stuff article):
Shellac - Not many people use shellac any more but it is a natural option. Made from the secretion of a lac insect in Thailand. Pros: Natural varnish and dries fast. Cons: Possible allergy risk for children's toys and has a short shelf life. Also not vegan.
A different blog states that Shellac is completely safe:
Shellac and Lacquer are evaporative finishes, i.e. they dry with no chemical reaction. When an evaporative finish is completely dry it is also completely non-toxic. In fact, shellac is often used as the hard outside coating on candies and pills.
All I can say from this experiment is that it works. I'm interested in hearing the instructable community's opinions on the subject.