Official Luthiers Forum!

I'm finally taking the plunge into HVLP spraying -- thanks to all for the great posts in the archives! I have 2 occasional issues so far:
- Fisheyes on recoats of the same spraying session. A few on a top or back, maybe every 3 coats or so (most coats are fine).
- White/congealed finish bits, about 1/8" long, sprayed on with finish. 1 bit every 6 coats or so.

Some details:
EM6000 thinned 5%, strained into cup, 30 minutes between coats, 3-4 coats per session.
HF's 'nicer' gun (94572) with separator (68246). Regulator on gun set to 22 psi with trigger, nozzle opened 1.25 turns. Cleaned after each session.
Portable compressor through 25' hose
Spraying outside (no booth), in shade

I understand fisheyes are caused by a contaminant, usually oil. Mine are mostly on recoats, so I'm thinking...
- Oil getting through the separator? I could try 2 separators.
- An oily dust particle landing on the finish while the last coat is drying. Is that a common issue when working outside?
- ?

I'm guessing the white/congealed bit is finish that has partially dried in the cup, then fell off? Maybe clean the gun and cup and restrain every hour or so? I clean the cup after it happens and it doesn't reappear, but not sure that was the real fix.

Thanks for any insight.

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David Malicky

Not sure if the change is from "previous spraying to HVLP" or from "another application method to spraying using HVLP". If spraying is new to you you might just be discovering how silicone in the shop ANYWHERE, from waxes to lubricants, can magically make it's way onto your project. Just a thought.

cheers

I was getting fisheyes spraying in a small booth with multiple oil/water filters in the line. I'm spraying PolyWhey which I find sprays very similar to EM6000, except that it goes on quite a bit thicker. Since my booth is in a corner of the shop the RH is right at 45% and the temp around 75F. The solution for me was to add a desiccant filter to dry the air.

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Steve Smith
"Music is what feelings sound like"

Spraying outside is likely the problem. Pretty near anything could be getting onto the finish and causing the problems. You could set up a mosquito netting tent to minimize the bigger chunks.

Thanks, all, for the replies!
Steve G, yes, this is my first time spraying finish. I've banned silicone from our shop, but perhaps it has crept in.
Steve S, interesting, so it sounds like vapor moisture that easily gets past the filter can cause it. I'll get a dessicant filter.
Barry, The net is a great idea. A wet body is indeed kind of begging for something to fall on it. Unfortunately I won't have a booth for a while, so am hoping to make it work outside.
Thanks again.

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David Malicky

I grew up in San Diego and did a lot of outdoor spraying on heavy diving equipment - just not guitars. Gotta say if you're spraying outdoors that's probably the best environment you're going to get, especially if you're a few miles from the beach.

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Steve Smith
"Music is what feelings sound like"

Use a air hose dedicated for spraying finish. A compressor with an oiler will contaminate a hose.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

Regarding the 1/8inch long chunks, make sure your pressure is high enough. If too low, the finish can collect on the tip of the gun, then break off and create a finish booger.

Thanks!
Todd, yes, mine was as you describe when I got it (they shorted me on the paper towel, alas). I thought I got it all but an acetone bath sounds smart.
Steve, good to hear. My spray location is ~4 miles inland and ~100 yards from some traffic, so maybe exhaust is an issue for me.
Alex, good suggestion and I have another hose to try, thanks.
Glen, that makes good sense, thanks -- I'll look out for it at the current 22 psi and raise if it's not staying clean.
Thanks again, all!

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David Malicky

What Todd said.........!!!
Tom

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A person who has never made a mistake has never made anything!!!