Great balls of Fire! (OK, just a hot weather lacquer question) - created 06-24-2006
Dotson, Mike - 06/24/2006.21:52:42
New and Improved. Same Low Price.
I'm spraying some McFaddens and having a little trouble with it 'dusting' (for lack of knowing the correct term). I assume it's drying too fast as it's about 105º-108º outside with the swamp cooler dropping that in the area near the shop door I spray at by a few degrees. Humidity is about 35% today.
I usually add about 15% thinner to it and haven't had this happen before. Should I thin it more or try some reducer?
So far I've just gone back after each coat and sprayed a light coat of thinner to melt it a little but I don't like doing that.
What's happening is probably your thinner is flashing off to quickly due to the high temperature. So I suggest adding some reducer. It would hopefully prevent the spray dropplets from drying before they hit the surface. You could also move the gun closer to the surface and/or slow down your stroke so the lacquer builds up wetter on the surface. Be cautious though cause any of these can also lead to sags/runs.
Thanks Barry. I started again this morning and all my reducer has been, um...reduced.
This one is especially problematic because I am spraying the raised fretboard (lap steel) and is has some other raised areas on it where the 'frost' is accumulating.
I've tried backing off the pressure, slower passes etc. and it helps to some extent but I have gotten a couple runs and heavish areas. I'm just doing the build coats this weekend so I'll be able to get some reducer before I get to the final coats.
On the positive side, nothing has a chance to get stuck in the wet lacquer.
Hey Mike, I can certainly sympathize with the hot weather problem. The dusting you descibed is common where I live as well, we both live in desert climates. Solvent based finishes can test you in that kind of heat. I have had that problem with synthetics as well as acylic lacquers plenty of times. Heat will make a problem like that much worse. Spraying ten to fifteen feet in the air during the summer and right next to a uninsulated steel roof was the one that gave me the most trouble. I had to use a completely different formula to get normal wet coat. The finish store gave me the wrong thickness reducer that made the finish prone to run but I kind of dealt with that and got the right stuff later. Yeah, I reamed them a bit about it, the 2k worth of finish work I was doing for my customer who was waiting for it to be done made me a little testy.
Orange peel can be caused by too quick a solvent flash as well. Any time you do not have a good flow-out it is cause to change adjustments, distance and speed of application. Sometimes a change to a slower thinner or reducer will help, or a retarder to improve the flow-out. For me it usually it is a faster solvent that will do that. I rarely if ever have the other things that cause that be the problem since those are gun adjustments or spraying too far away. Barry is the nitro lacquer guy not me and his advice is pretty sound as usual. But if you are still having the dusties after you follow his advice, think about a slower thinner/reducer or a retarder. I checked McFadden's site for the related problems of lack of flow and orange peel which are also heat related and those are remedies they are recommending for that.
Thanks RP. Yesterday was even worse, then in the evening we had a little dust-up and some moisture moved in. By 7 or so it had dropped into the 90s (mmm, nice and cool) and I got a real nice coat on to end the day. My new HVLP is a joy to use when the conditions are right.
I'll just have to work around the weather on this one and get some more reducer.
Dude, I so feel your pain. Solvent finishes are a (long string of expletives) in the heat. If they did not have that look, it would not be worth it. The only thing that works is to slow the solvent flash. I do not know if it is practical but, cooler nightime spraying can be pulled out of the bag of tricks for serious heat hassles. Yeah, the bugs..........
I think that HVLP is the reason it is not a total drag. They flow a lot of finish and that can help in the heat a little. Let me know how it works out.
The stuff I was spraying in my little story (a polyurethane) will pretty much flow-out in most any conditions and humidity levels. It is utterly amazing. That was the first time in 20 years of watching myself and others spraying it, that I had ever seen it dust up like that. Normally it will flow out so well, you have to watch it close or it will run like water. If you are the least bit uneven with the second coat it will sag or run. You get used to it and it is second nature after a while, but if you get lazy................
If that got the dusties, there is no way I could have sprayed a solvent finish at all.
I won't spray Nitro in really humid conditions. You can do it even with the worst summer humidity but you'll have to put in a lot of retarder which will slow down the drying and curing rate of the finish. A heavily retarted finish even though its will be dry to the touch will outgass solvent for two or three times the normal rate. So where you might rub out a normal nitro finish in 2 weeks you'll need 4-5 so as to minimize shrinkage and gloss dieback.
I've been using a capful of butyl cellosolve to a quart of nitro, and then using the Rival hot water pot as a warmer for the gun. Spraying at about 120 degrees lacquer temp plus a little retarder does help with blushing (which is the problem here in the soggy East). Does take a little bit longer to set up, but 4 weeks is plenty of time to get everything ready to buff.
"Rival hot water pot as a warmer for the gun."
That must be siphon gun or I need a picture or short explanation.
Hi Mike,
It's a Turbinaire bleeder, which pressurizes off the turbine feed, but has no check valve. A few inches of water in the Rival, and let things warm up for 30 minutes. With the pot set to about 150 deg F, I get 120 deg lacquer temp which helps in flow out and keeps the surface temp from dropping below the dew point and causing blushing.
Or at least it seems to help...
With a gun that has a one-way check valve to pressurize the cup, I'd probably crack the cup seal when it's heating up.
Thanks everybody. Lowering the pressure, sloooow passes and shooting just before 7am has really made a difference. Getting by without any retarder.
Not sure how the neighbors feel about the 6:45am compressor fire-up, but this makes up for their kid regularly skateboarding and playing basketball at 11pm.
Lowering the pressure, sloooow passes and shooting just before 7am
Sounds like a sensual way to start one's day.
Ellie you're a dirty, dirty grrl!
Just in my mind, Mike. In real life, I am the picture of decorum and delicate sensitivity, a frail flower of semi-victorian reserve.
People have described me the same way.
Oh, sure, both of you.........
"of decorum and delicate sensitivity, a frail flower of semi-victorian reserve."
This statement somehow flies in the face of "Great balls of Fire". (or vice-versa)