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Posted this once, but it did not show up. If it posts twice, sorry! For anone using pure butyl cellosolve as a retarder, what have you found to be the max mix ratio of lacquer, thinner, and butyl cellosolve that you can use without creating issues?. I use a lot of retarder because the humidity is always very high here, I normally use Sherwin Williams retarder thinner, but am inerested in trying pure butyl cellosolve. I'm talking about combating blushing in very high humidity. Thanks, Bob

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Generally you want to keep Butyl Cellosolve under %5 of the mix. A couple of other things you can do is switch to automotive thinner and possibly add some MAK.
I try not to add retarder if I can avoid it. If I am getting blushing I will often move the item to a warmer environment (lower humidity) or use hot lights.
A brief article on solvents that explains their use much better than I can:
https://thefinishingstore.com/blogs/new ... er-thinner

Clay- Thanks for the response. Good article on thinners.Over the past 40+ years of spraying nitro, I've tried about everything. I've done over a thousand finishes, plus repair work when i was doing that. I've done everything from spraying out my door into a North Cascade snow storm to my current issues of having to spray during a torential rain in the rainforest I currently live in. Spray booths, albeit not the best of them, lights, dehumidifiers, I've tried them all. Never have found the absolute answers, but retarders have always been my go to cures for humidity issues. Since most of us lack total control of our spray environment, I suppose that is a big part of the picture. The article advice, and yours, about automotive thinners sounds interesting. Not sure what MAK is, so will have to check that out. Thanks. Stay safe.-Bob

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“ The meaning of life is to find your gift and the purpose of life is to give it away” Pablo Picasso

MAK is methyl amyl ketone. You can sometimes find it at big box stores or from paint supply stores in reasonably small quantities. It is a slower solvent, but not as slow as Cellosolve, so it may allow the trapped water molecules to leave before the lacquer has dried, but still not retard things as much. It may also allow the lacquer to "hang" better than cellosolve does.
Finishing is as fickle as the weather, and weather is often the cause of that.

I just use the rattle can of retarder (used to be Behlen, now Mohawk) and hit it a light coat immediately after spraying with Nitro. Works every time even in the Soggy Bottom of Orange, Tx. I don't know if it contains "cellosolve" or not.

I used to add a little cellosolve to my thinner to avoid blushing. I ran out, sprayed without it last week, had some blushing and tried a light misting with a Mohawk anti-blush rattle can.

Instant fix. I’ll just use the can going forward to treat symptoms if and when they appear, rather than fool around trying to prevent them by guessing what percentage of retarder to add to my lacquer based on the weather.

Just a further note on butyl cellosolve use. We often see mention of re-adhering lacquer around tuner, screw, or other free edges in the finish, as well as minor spider crack repair using bytyl cellosolve. It seems like the majority of these threads include some report of difficulty in ensuring adequate wicking, with incomplete or spotty penetration resulting in the need to open the resulting pockets and reapplying the BC.

One technique we used regularly with BC was to cut it 50/50 with lacquer thinner, dramatically reducing both viscosity and surface tension, with significant improvement in penetration. In many cases, it was not necessary to open a check to get full penetration, and we saw no real difference in how well the BC remelted the lacquer.

With regard to BC in lacquer, we seldom used it, preferring to avoid RH above 65% during spray operations versus having to add time to the finish process due to the softer, slower-drying film when additional BC is added to the finish material.

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Mohawk's no blush + retarder is a combination of some faster solvents and MAK. I didn't see any butyl cellosolve listed on the data sheet.
It is primarily designed for furniture repair techs doing touch up work. The fast solvents soften the surface, the MAK sticks around long enough for the water to leave, and then the surface rehardens. Most of the blushing we see is on the surface, but in really humid rain forest conditions the blushing can go much deeper and butyl cellosolve may be a better option even with the drawbacks it creates.

Thanks for all the replies again. Certainly spraying at lower humidity is the optimal environment for finishes. However, if the humidity ever drops below 60% here those are desert conditions for us and it seldom happens. Keeping the shop dry room at 45-50% is easy, but a dry spray space is more difficult. Take care.-Bob

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“ The meaning of life is to find your gift and the purpose of life is to give it away” Pablo Picasso