I use food colors exclusively for my colored puzzles.
But remember this: Nothing difficult is ever easy!
It has taken me 10 years to perfect my process and I continually tweak the process.
It would take many pages to describe my process.
Softness of wood is an issue so I test every piece of wood I buy with a durometer. I have discovered a hardness setting below which I will not buy a piece of wood. End grain bleeding is a problem with softer woods.
Some colors work better diluted with water; some with alcohol. Some colors will change color when diluted with alcohol.
Some colors require a different application technique. Some colors can be dipped - some colors work better being wiped on.
Then there is the sealing situation and what sealer to use. Some penetrate more, some dry faster, some require more than one coat.
But it is important to seal the food colors into the wood with a sealer such as lacquer, urethane, etc - picture a young child putting unsealed puzzle pieces in their mouth and then putting the pieces on an expensive white leather couch! Both the child and the couch will be colored. And I guarantee that purple is permanent and can't be removed from the couch. And you can't buy liability insurance to cover any damages!
And the list goes on and on!
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