I’ve worked with a lot of different oil & veg tanned dyed leathers and the etched areas will look different even if it’s the same tanning process due to the dyes. And sometimes even varies lot to lot, or even hide to hide of the same leather “color” & manufacturer to add even more variation to an organic & therefore less consistent material.
But it’s what I work with most of the time–both making goods and adding my logos and designs to them.
It’s unlikely leather for a dog collar is chromium tanned due to the types of leather and applications chrome tanned is suited for, but best to confirm from your supplier, as it’s not safe for you or your machine to etch it.
You should be gently washing the soot off anyway–else it will get on customer’s fingers and they’ll be very unhappy.
And definitely remove any soot before you try any painting–else you’re just adding paint over the soot, and it’ll come off when the soot does (or even before, since may not stick to soot), and still not produce the effect you want. Might look great in your studio, but as soon as it’s touched and handled, it won’t look like you wanted it to & again, unhappy customers.
I’ve never had success masking & then trying to paint in the etched areas–spray paint may work–but anything liquid will tend to bleed into the porous flesh of the leather and may destroy the clean lines produced by the laser… (I usually don’t mask for my etching, and if I did, it starts to come off when wash off the soot, so doesn’t stay in place well enough to function as a stencil…).
But pending the finish the supplier is using, if you’re willing to test one of the pink, or another that doesn’t produce the contrast you want, the top may be treated so it won’t absorb any paint, and you can quickly apply something into the etched lines and it cleans off the unetched finish…
And sometimes just Mink Oil (or other leather conditioner of your choice) will help darken the now exposed leather of the etched lines to provide more contrast.
