Staining wood blue with chemicals

Question

I know about the process of 'ebonizing' wood (using steel wool + vinegar to turn wood black), and I have seen excellent results using this process.

I was wondering if it is possible to use a similar method to stain wood blue instead.

My first thought was copper sulphate, then drying it off and maybe the crystals would form in the wood, making it look blue, but apparently it makes it green instead (understandable based on the green rust of copper).

So does anyone know of any chemicals that can be used to stain wood blue effectively? I would like to avoid using typical dyes or stains, as I find they can be very expensive and not always have good results, when ebonizing has worked wonders.

Answer 1

I know there was discussion of indigo up in the comments, but that was based upon going through the entire process of growing the indigo, then fermenting it to use it as a dye. Although there can be a lot pleasure in going through an entire process like that, there is no reason you would have to. Indigo dye crystals (both natural and artificial) are inexpensive, readily available and easy to use (as opposed to many other natural dyes).

I have never used indigo on plywood, but it does a great job of dying basket reed, and is dark enough to make a blue color even though the reed is not white. Here is a couple of pictures from an event I where I taught a basketry class. You can see the color of the material, and a finished basket in the foreground.

A couple of my students dipped their basket in the indigo dye pots (it was a weekend retreat--there were alot of crafty activities occurring). Here is a picture of two baskets--the one in the foreground was only dipped once, the one that is darker blue was dipped multiple times. Ignore the yucky looking caked on stuff at the bottom--the basket maker was experimenting with the indigo foam.

Answer 2

Methylene blue is a very effective water-soluble blue dye and you can buy it on amazon quite cheaply (the pack at that link is probably enough to dye a table and chairs). That might do the trick. It's also used for treating fish in tanks, so is quite benign. The question becomes one of whether the water raises the grain too much given that the dyed layer is likely to be quite thin. It's also soluble in alcohols (including isopropanol, so surgical spirit/rubbing alcohol) which wouldn't raise the grain.

I've done a quick test on a bit of scrap softwood using something like a 0.7 mmol/l aqueous solution (0.2 grams per litre of water). It was brief enough to not raise the grain even where I left it on the longest:

I've adjusted the colours to look about right on my screen. The wood was quite old and yellowed. It had just about dried when I took the picture.

The left for 1 minute test was meant to simulate dip-coating. I didn't hold it very steadily, so the unevenness below the "p" in the annotation was casued by the solution running.

It could work nicely, but you would want to make sure the wood is very white to start with, and stays that way, to keep it really blue instead of turning greenish. This is probably true for any blue dye. This article on bleaching wood implies that you can bleach the original wood with the right wood bleach, then neutralise and rinse and there shouldn't be any bleach left to react. Here's some more discussion on bleaching and coating so it doesn't turn yellow; in summary: use a water-based varnish over the top so the varnish also doesn't turn yellow, though pine will yellow slightly whatever you do.

Of course, test as much as you can on scrap (and the same type of wood) first, in particular if you decide to bleach then dye.