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Changes to the PR-1 usage recommendation

Posted: Fri Sep 21, 2018 5:21 pm
by jmurray2112
The original post on this topic was lost in our recent web-hosting migration. Since the original posting, I've had a fair amount of time to test our new recommended carrier for the PR-1 resin, and the results (at least for me) are pretty conclusive.
Once upon a time, our PR-1 resin was very friendly to water-miscible solvents like denatured alcohol or acetone. It tolerated them well, with no swelling or application issues like surface agglomeration (little bits of hardened resin clinging to the leather surface) when the primer mixture was rubbed on. Then, about five years ago, there was an industry change to resins like this. They were originally primarily siliconized acrylics, but then the big chemical companies that produced them decided that silicones were too expensive no matter how effective they might be, and decided to mix urethanes with the acrylics instead. Then, they passed on their savings by doubling the price. Can you tell how I feel about big chemical companies? :x .
However, our cleaner is a much better carrier than alcohols or ketones. The citrus solvent in it is a oil-based solvent (organic solvent), but because the cleaner is an emulsion (combination of normally incompatible components like oil and water), the PR-1 resin interacts with it just fine, with none of the swelling or surface agglomeration described above. I do a lot of priming of unfinished veg-tan leather, and the difference between the two types of carriers is pretty dramatic, and really speeds up production because I don't have to sand or strip off the little residual bits of primer prior to finishing.
So, I recommend using either SG-4 ready made, or make your own using our cleaner and PR-1 concentrate. SG-4 is basically 3 parts cleaner to 1 part PR-1 concentrate. If you make your own, you can also load in the PR-1 (up to 35%) if you are priming a really thirsty aniline leather, or are converting a nubuck to a finished leather. Let me know if I can provide clarification or more info.

Re: Changes to the PR-1 usage recommendation

Posted: Mon Mar 16, 2020 8:47 pm
by jmurray2112
Here's an update to the PR-1 usage. Our most recent version of PR-1 has changed yet again. Happily, the newest version is now interacting quite well with denatured alcohol again. Yay! That's not much help to techs in CA, where it's much harder to get DA now, but for the rest of you, DA is once again a good candidate for mixing with PR-1.
I did test it with acetone, finally, and it was ok for about 5 minutes, before it started to get stringy and chunky, so no joy there.

Re: Changes to the PR-1 usage recommendation

Posted: Mon Aug 24, 2020 3:33 pm
by jmurray2112
Another update for techs in CA, or in other places that can't get denatured alcohol anymore. I've tested PR-1 with Isopropyl Alcohol 99% and 91%. While they both swell the resin somewhat (thicken to near a gel), it doesn't seem to affect application at all, and I don't see evidence of it leaving those irritating little nubbies I talked about in my original post. Of course, the COVID pandemic has made it hard to get either IPA 99 or 91 because everyone and their brother has been making hand sanitizer with them, but at least they're not banned, and I imagine production will eventually catch up with demand. Heck, they are selling drums of pre-formulated hand sanitizer at Lowes now, for Pete's sake.
I didn't bother to test PR-1 with rubbing alcohol (IPA 70), because at that dilution you lose solvent aggressiveness, but it may work in a pinch.
The swelling can be advantageous, actually, if you are priming a delicate leather like calf or kid-skin, in that the resin won't penetrate as far into the fiber structure, potentially reducing stiffening of those leathers.
Anyway, there you go.