Spraying large sheets - Woodworking Talk

Brent Luck · 07-08-2009, 06:53 PM

I am spraying 4x8 sheets with laquer and am coming up with streaking in final finish. I am overlaping 50 percent but it doesnt quite even out when dry and you see streaks at an angle. I have added a retarder to slow dry time. What else?

Brent Luck · 07-08-2009, 07:05 PM

Quote:

Originally Posted by Brent Luck

I am spraying 4x8 sheets with laquer and am coming up with streaking in final finish. I am overlaping 50 percent but it doesnt quite even out when dry and you see streaks at an angle. I have added a retarder to slow dry time. What else?

Would rubbing out finish blend streaks out?

cabinetman · 07-08-2009, 08:39 PM

Are you spraying flat or vertically?

Brent Luck · 07-08-2009, 09:32 PM

I am spraying vertically.

edp · 07-09-2009, 03:06 PM

but when the warmer weather comes, I cut my lacquer with lacquer thinner. Generally 2 parts lacquer to 1 part thinner for air atomizing guns (HVLP conversion). This keeps it wet enough to avoid overspray and streaking.

Ed

Brent Luck · 07-09-2009, 03:51 PM

Thanks, I will try

**Leo G** · 07-09-2009, 03:55 PM

What kind of a gun, what product are you shooting, how are you thinning (% or parts per #'s), what size tip, how wide of a fan are you achieving, are you box coating?

Brent Luck · 07-09-2009, 04:08 PM

It is a Hvlp turbine with a 14 tip. spraying Mohawk duracoat lacquer 20 sheen. I am not thinning but am using a retarder. 6 inch fan onto flat sheet standing vertically.

**Leo G** · 07-09-2009, 04:15 PM

If you have a 1.7mm tip I'd switch to that. If not you need to thin more. Using retarter IS thinning, it is just a slower drying thinner. Sounds like you may have an uneven fan or a graduated fan. Take a pc of brown paper or cardboard and hang it on the wall. Put the gun about 8-16" away (whatever you do) and shoot a short burst. Look at the pattern. Is it even? Or is it heavier in the center and lighter on the edges. If that is the case you need to thin more or add more air.

**Leo G** · 07-09-2009, 04:20 PM

Wow, that stuff is thin already. 15 seconds on a Ford #4 cup. It should be thin enough to spray right out of the can. Sounds like you either need a bigger tip or have to spray with a slower motion. You must keep a wet edge. Spray from the top and go down.

Brent Luck · 07-09-2009, 04:27 PM

Quote:

Originally Posted by Leo G

Wow, that stuff is thin already. 15 seconds on a Ford #4 cup. It should be thin enough to spray right out of the can. Sounds like you either need a bigger tip or have to spray with a slower motion. You must keep a wet edge. Spray from the top and go down.

Ok bigger tip. What about what I see now can I sand and recoat and will that blend out

**Leo G** · 07-09-2009, 04:31 PM

It depends. If the streaks are because you have an uneven soaking into the plywood, it might show, especially if it has been more than 24 hours. If it hasn't been too long you can respray and it will remelt in and blend well. If you are just clearcoating give it a good agressive sanding with 320 and your RO sander. If you have stain on it then you will have to just do a light scuff and hope for the best.

I use MLC MagnaMax and the out of the can viscosity is arounf 35 in a ford #4 cup. Your Mohawk lac is substantially thinner than what I am use to spraying.

Brent Luck · 07-09-2009, 04:42 PM

The pieces have already been stained, sealed, glazed, sealed and have a 2 coats of lacquer.

**Leo G** · 07-09-2009, 04:45 PM

Looks like your only choice is to scuff and apply. Remember to keep your final dry mill thickness at 4 mil or less.

Brent Luck · 07-09-2009, 04:49 PM

Thanks Leo G. You have been great help. Obviously I am new at this. I dont know how to check mill thickness

**Leo G** · 07-09-2009, 05:02 PM

You usually guesstimate it. If you have 25% solids (volume) and you spray a full wet coat (4-5mil) after it dries it will be around 1 mil. So you can do 4 full wet coats and after it dries you will have a 4 mil dry coat. Sanding and thinning of the product makes the coating thinner so you have some leeway. If you put the coatings on too thick they have the chance of cracking after a full cure (usually around 32-30 days). I have never had this problem and I know I have done some thick dry coats. It is more of a problem when you use post cat lacquers as they have a much more aggressive catalyst and are a harder and more brittle coating.

Here is the spec sheet for the Mohawk Lacquer you are using

Brent Luck · 07-09-2009, 05:15 PM

what about rubbing with steel wool. do you think this would blend some of this out.

**Leo G** · 07-09-2009, 05:17 PM

Without seeing it I would just be guessing. I would use a scotchbrite pad instead of steel wood if I did though.

Brent Luck · 07-09-2009, 05:23 PM

Thanks so much Leo G. I am starting to think some of my problem is the temp he in Arizona. I am going to get a good and early start at the coolest part of the day in the morning and go for it. If that doesnt work

**Leo G** · 07-09-2009, 05:27 PM

If you put your location in your file it would help give clues. The retarder is probably a good idea. If you could lay the sheet flat it will slow the drying down some and maybe alleviate some of your problem.