Hi, unfortunately once the paint is on, the dye has nothing to soak into... I agree that dye would have probably worked better than paint.You could try removing the paint, but usually the acrylic leather paints are frustratingly durable.If it were me, I'd be inclined to make a little art project out of them and paint them something fun and colorful using Angelus leather paints (http://www.angelusdirect.com).
Leather is naturally water resistant, that doesn't come from the dye. If you deglazed the boots then dyed to black you wouldn't fundamentally change that. What you'd probably want to do though is use a good waterproofing product on top - I'd probably go deglaze -> dye -> condition -> Obenhaufs LP -> black wax polish to get something both highly water resistant and still shiny black.All dye projects are experimental, but going to black is pretty low risk, I wouldn't hesitate to do it on my work boots (which are, like yours, quite expensive..).
The Angelus suede dye would be right for this - you could skip the deglazing (though give them a good cleaning first with some unscented handsoap, then allow to fully dry with some shoe trees in them to hold the shape), and then after dyeing you wouldn't polish, so you'd keep the matte look.
Nice work, those look much better now! I didn't notice much color shift, but they do change a bit, particularly as the oils and things from the polish soak deeper into the leather. The lighting can also have a big impact on how red they look, particularly with the cordovan colored dye.
Angelus sells a "neutral" dye which is the dye with no pigment, it is used for exactly what you are describing, thinning the dye out for more translucent effects. As always, practice on some test pieces, dye is always unpredictable in how it interacts with different materials.
I'm not sure, if they have a shiny finish, then you may want to deglaze them still. If it is a matte finish, then the paint might hold fine.Nail polish remover is mostly acetone, but also has other junk in it like fragrances and stuff to make it less harsh on your hands, it might work in a pinch, but not ideal. If you have a farm and ranch store or a little hardware store around you I'm sure they'll sell it, but I don't know how rural you are. ;)
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