Collated from newsgroup postings.
I would like to take a piece of birch stock and permeate it with a colour (colour not important at this point since I am just exploring this idea). For example let's say that I want to turn the block of wood purple. What dyes would I use and how could I get them to transfer/migrate throughout the piece of wood?
How could I dye the wood green (or red)?? I would like to do this before turning because I think the process might distort the shape of the bowl if done afterwards..
There are no easy answers to your question. There is only so much that you can do with natural absorption at atmospheric pressure. You are going to have to experiment.
Get an aniline dye, mix it to double the concentration recommended by the manufacturer, heat it to just below boiling point, submerge the wood in the solution and keep it warm for 48 hours. Remove the piece of wood, wipe it dry on the surface, cut it in half, and see what happened.
Black is the easiest dye colour to use. I have always been disappointed with the results of the primary colours unless I bleached the wood prior to the dye job.
You will find that some species work better green than dry. Others, like Oak and Ash will penetrate through the end grain easily but almost not at all cross grain. Holly is by far the easiest wood to dye. Basswood is a close second. Mahogany dyes well, but you will have to adjust the dye to compensate for the red wood colouring. Birch veneer dyes well, but the solid wood tends to get a blotchy appearance. Maple does not accept dye very well, but that will depend on the variety, and where it is grown. So, again, you will have to experiment.
If you want to read about using the various dyes, get the book "Colouring Techniques For Woodturners", by Jan Sanders.
You should rough the piece first, so that you don't have any overly thick sections. If you rough it green, there should be no added distortion from permeating it with water-based dye. Then again, if it was finish-turned and dry, oil based dye should not cause any problems, either, and all the expensive fuss about getting good penetration could be avoided.
If you really want it well penetrated with dye, you will want put the wood in a vacuum chamber. For best results, you need to suck the air out of the wood and then submerge it in dye (still under vacuum). This will require a chamber with some means of either moving the wood or adding the dye without opening up the chamber. When the wood is submerged, you can let the vacuum off. Be sure that dissolved air has come out of the dye (if you're adding the dye to the chamber, which is simpler than moving the wood), an initial "boil" works ok.
If you build this setup, you will also be able to make oil-impregnated wooden bearing parts (the process is basically the same - substitute "oil" for "dye" in the above). You can also make epoxy-impregnated "fake tropical wood" if you get thin epoxy (and have fun scraping it off the chamber walls). Epoxy-encapsulating electrical circuits was my introduction to this process.
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