Borax for Darker Etches

Applying a solution of borax-in-water to wood can produce a darker laser etch.

Today Danny and I were testing ideas on Tarkin. I happened to have just come from buying a box of “20 Mule Team Borax” as any history-loving laser nerd is prone to do. With this known darkening agent in-hand we messed around with it while testing many of the rastering Image Modes available in Lightburn.

Baking soda is another darkening agent and it definitely works (compare left and right images). All these were etched on the same birch ply using the same image set-up. Of the three, borax was the most effective darkening agent. Give it a try!


So this was etched, then the borax solution added? Or is this done pre-laser?

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Apply borax solution to the wood, allow it to dry, then laser etch.
We didn’t explore the proper borax concentrations.
Similar process applies to baking soda.

Yep I was surprised. I’d seen some online comparisons of borax vs baking soda, and the general result seemed to be that borax was a darker yield, but it was sooty, not stable, and didn’t hold detail as well. I’ve been using baking soda in water solution, it’s in a labeled sprayer in the cabinet. Plus a drop of dish soap as a surfactant to help it soak in.

This result with borax looked fine! The detail was there and it was not loose soot. It was deeper than the baking soda contrast solution in the sprayer. However, the baking soda was diluted for the sprayer whereas I think the borax was sort of rubbed on as a slurry and rinsed.

I took a pic of the borax experiments at the end of the day. The bottom left one ran past the line where the borax was applied, and, like with the baking soda, you can really see the difference!


This is a technique I’ve been wanting to experiment with as well.

I’m also curious if y’all have any experience with applying stains/finishes to the end result? Generally speaking, engraved wood tends to get minorly-enhanced contrast with most finishes I’ve tried, but I wonder whether the borax treatment significantly changes that or otherwise significantly affects the process?

@J-LoM, borax can’t be bought in small quantities at local retail.
Why am I telling you this? Because I’ll NEVER use all that I bought.
If you’d like to experiment with borax then please use as much as you like.

The borax box is on the top shelf of the resource cabinet in the laser room.


What’s the mechanism of operation?

People presume Maillard reactions, but I don’t think that’s actually proven. Both borax and baking soda are alkaline (note: borax is not boric acid). I don’t know how people arrived at these options, maybe someone sat down and tried every household product on the shelf?

My first thought was that if it’s a pH thing, what’d happen with a lye solution?

Pretzels turn out much darker with a lye bath than with baking soda…

Yeah I wondered about lye, AFAIK no one’s tried it. It might get darker still, but we don’t wash off the wood afterwards so I wonder if it would affect the wood over time, including that which was never burned with the laser at all. BTW both baking soda and borax do darken the wood right after it’s applied, it shows up in the photo I took. Those have been used enough that we’d know if the wood darkened or degraded over time.

I do have some pure powdered lye here and can make a 4% solution like they use to dip pretzyls. Lye is kinda dangerous to use, though. Diluted, maybe not so bad, but making a mistake with pure baking soda probably never melted anyone’s flesh.

FWIW - borax can be used for a fair variety of tasks. Often cleaning oriented, but it’s one of those things that is more broadly useful than one might initially think.

Probably. :slight_smile:

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Excellent info. Any issues with grain raising? I’m assuming this is applied as a water solution.

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Good question. Also interested in that aspect. And if it does appreciably raise grain, I wonder if that can be sanded off while still maintaining enough penetration for a clean effect.

Yes, mixed it with water is what we did.
That said, the was no dilution logic to our test.
Furthermore, there may be other solvents that work.

If you do any borax testing then be sure to share what you learn!

I haven’t seen any grain being raised; I would just use a spray bottle and let it dry

It does leave wood a little darker. I don’t think it’ll wash off back to the original color after burning.