Thread: Lacquering Nightmares

Get yourself a cheap little Handysprayer from CIG and your spraying woes will be solved......... low pressure..........

It seems to me that your gun pressure is too high and that there may be water in the lines and also that you are not thinning the finish adequately.
I suggest you do a Tafe course on furniture finishing or a panel spraying course.

Check out your local libruray you might find a text on spraypainting there.

there have been some farely heavy discussions on the subject here from time to time do a searck & chek em out.

cheers

Richard
step 1, get a tech data sheet from the lacquer manufacturer, I use Mirotone it's pretty much fool proof. 100psi is way to high, even for a poor quality gun. Make sure you use a good quality filter/drier/regulator. Try that for starters, you'll probably get a huge increase in quality. Post more Q's later, if needed.

Mick

Originally Posted by Richardwoodhead

As a retired geologist not formally schooled in woodworking, I've managed to master a lot of the "trade". However I'm having lacquer spraying nightmares. Even with an expensive spray booth I'm getting streaks, roughness, splotches, white spots, crinklyness, lacquer fragments, etc. Mastering the settings on the gun has helped. And I'm about to invest in a pressure pot. My compressoer is at 100 psi (too high?).

Lacquer finishes are fantastic, but there's obviously an art and science to it that I havn't mastered yet. Any suggestions?

Gooday. all of the above answers are right.

Set the pressure down to about 60PSI.

Streaks are generally caused by pressure too high (drying lacquer before it hits the workpiece), moving too fast, not keeping a constant distance or not enough overlap.

Roughness is generally caused by above as well although on some timbers the first coat will raise the grain and need to be cut back before the next coat goes on.

Splotches can be caused by water from the gun via air lines. It can also be caused by a dirty nozzle or loose fittings allowing a variance in pressure. Also technique. Hanging about too long in one place.

White spots are generally over spray. You get it sometimes in corners where a "dry mix" adheres to a dry surface. Can sometimes be rubbed out but most times needs a wet spray over the top to blend.

Crinklyness is too much air hitting a semi dry surface and putting waves into it or silicone contamination.

Lacquer fragments. Strain it through a stocking after it has been removed.

Hope this helps. There is an art to it but it is easily learnt if you practise.

G'day Richard,

What sort of gun do you have?
If you don't have a Star 770S do yourself a favour & buy one, about $60.
The Star is a great gun if you are learning!!!! On the bottom of the gun is an air screw so you can adjust incoming air. Don't get technical about air pressures as it's all up to how the gun is setup. I run my compressor @ 125 psi & adjust air @ the gun.
The most simple way to get correct atomization is to turn the air screw on the gun so there is no air flow. Adjust the air screw while pulling the trigger until you have a fine, full spray, not too much air is required. On my touch up gun that's got no air screw I use about 22 psi to spray lacquer.
I was taught this trick by a professional furniture maker/restorer & it's simple & reliable.
When you have a bit of experence look into HVLP guns. A pressure pot complicates the gun setup & atomization pressure. Too much pot pressure is the usual problem people have.
I hope this helps

i would keep pressure right down. thin your laquer

Thanks for the feedback. Went up to Perth from Margaret River the last 2 days to pow-wow with Becker Acroma. Have been using their DM307 lacquer and Iwata 7700 gun. Have upgraded to a pressure pot with Iwata 200 pressure feed gun, and pressure regulators and filters (for water & particulates) so I will now be using lower pressure, "cleaner" lines and supposedly a superior spray feed. Have been diluting with 30-40% thinners, so I think the main problems, as you all noted, were too high pressure, dirty lines and incorrect fluid and air settings on the gun. (This woodwork forum is amazing! Thanks for your input..)