Quote:
Originally Posted by Quickstep192
Thanks for the replies. I'll definitely try the mix of piano lacquer and stringed instrument.
I tried spraying the Stringed Instrument Lacquer full strength, then at 20% reduction, then at 25%. It seemed that no matter what I did, I got a lot of orange peel and bubbles.
Long story short...
I decided to "go for broke" and tried a mix that was 50% Lacquer, 43% Thinner and 7% Retarder. It seems to be working. It seemed to spray easily and even though it builds very little per coat, I can probably do four coats per hour.
Is this too thin? Is there heartbreak waiting around the corner? Is it reasonable to think that I'll need double the number of coats that would have been necessary at full strength?
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I think viscosity & retarder are not the problems. I've sprayed this stuff straight and/or thinned about 15% with excellent results.
However spraying is not easy and there is a learning curve for each finish...
First get the room temperature, wood temperatures, and finish temperature right. My room is about 20 to 22 deg C. Too cold or too hot causes problems. Too humid also causes problems.
Second, using a viscosity cup and your gun's operating manual determine the tip size that your gun requires. I gave viscosities for the finishes I use to my supplier and he recommended tip sizes for me.
Third is the hard part - and for me it was trial and error until I got the hang of it - you must develop your spray technique; and the technique might be different for different finishes. e.g. when I spray water based finishes, my gun speed is much (~50%) faster than when I spray solvent based finishes - because the water based solvent has higher viscosity and requires lower coating application thickness.
- If I hold the gun too close to the surface I get orange peel. My gun recommends 8" from the surface. Take out a tape measure and check how close to the surface you're holding your gun.
- If I spray a coat too thick I get orange peel (i.e. if I move the gun too slowly).
- If I spray with insufficient pressure I get orange peel/poor atomization.
- If I spray too many coats too quickly I run into problems - either orange peel if I go back and re-spray over wet surfaces (i.e. coating is too thick), or I've ran into a variety of curing problems if I didn't let the finish dry between coats.
- If I hold the gun too far away from the surface I get a dry pebbly finish.
- If I spray with too much pressure I waste finish and get too much overspray.
- If I spray too quickly the coat is too thin, it doesn't flow out, and I have to spray more coats to build-up.
I had a lot of trouble until I got the first two points right (holding the gun 8" from the surface and moving the gun at the right speed to get the right coating thickness). It's frustrating, but you must find the right combination of pressure, tip size, spray distance/spray speed/coating thickness that works.
Once you figure that out you can very good results from this finish.
p.s. like you I've found that I get better results using a smaller tip size and slightly higher pressure than my supplier recommended - but this is inter-related with viscosity and coating thickness. I suspect a professional using a larger tip and lower pressure can do the job much faster or with fewer coats than I can.