View Full Version : Finish Disaster

08-05-2013, 02:39 PM
I decided that I would try a lacquer finish with my two latest sopranos. I got a few quick coats on and then waited until the next weekend to do a second round. I started to spray and noticed something was wrong. As you can see from the picture the finish is cloudy. Any advice or wisdom would be greatly appreciated.

The facts....
1. Outside temperature 80deg F . I am spraying in my garage.
2. Cardinal Spray Lacquer. New, same quart as 1st coats.
3. A "better" quality Chinese touchup gun at about 50psi.
4. I practiced with just thinner and had what I thought was a good spray shape.

Moore Bettah Ukuleles
08-05-2013, 03:09 PM
What am I seeing in the pictures? One looks fine. In any event it looks like like some serious blushing. No problem, you can either sand through it or spray thinner over it under the right conditions. What are the right conditions? Warm temperatures (80 is fine) and low humidity. Because I live in a rather humid environment I run a dehumidifier in my spray room while I'm spraying. Adding some retarder ( up to about 5%) to the lacquer/thinner mix usually reduces blushing. (You didn't mention your thinner ratio.) Blushing is caused by moisture being trapped in the lacquer before it has a chance to dry. (Most noticeable when applied too thickly.) Retarder lengthens the drying time. So watch your humidity when spraying and try adding retarder to your lacquer.

08-05-2013, 03:24 PM
Chuck, Thanks for the reply. The one on the right only has two coats from the previous weekend. The one on the left was the one I was adding coats to. I was using the Cardinal lacquer straight out of the can. Also just to be clear because I am a beginner at spraying when you say "retarder" you are not talking about adding thinner correct ?

Moore Bettah Ukuleles
08-05-2013, 04:35 PM
Well there's your problem. I think you're going to have trouble spraying directly for the can without thinning. You'll have much better results after you thin it. I'd start with 30% of the same brand lacquer thinner and adjust from there. I reduce mine much more but my equipment is different than yours. Lacquer retarder is a slower drying thinner that does what it sounds like it should do. Also, those inexpensive door jamb guns work better at lower pressure, maybe 40#. And if you don't have an inline water filter or trap you should think about getting one.

08-08-2013, 06:50 AM
atmospheric humidity is one source for moisture I the finish, the compressor is another if it is not correctly used. Compressors collect moisture from the air, and can put it right back into the finish. Chuck mentioned the inline gun filters, those are a great, inexpensive, and are should be a backup, last line of defense from contamination in air lines. Shop air plumbing is very important. Coming off the compressor into a vertical stand pipe, 3/4" copper works well for this, into a 'T' fitting, with a 1/4 turn drain on the lower leg to periodically release trapped moisture. The theory of the metal vertical standpipe is that the (hopefully) cooler temperature of the vertical metal pipe will encourage condensation as it enters the pipe. The top of the stand pipe steps up to 2" galvanized pipe sloped at a gentle angle on the wall near the ceiling. Air going into the lower angled pipe slows down, and moisture condenses even more, and since it is sloped towards the vertical stand pipe, condensed moisture drains back into the vertical pipe. As long a run of this as possible is good, or at least 15-20 ft. Then another vertical 3/4" copper drop, provides air to workstations where you want air, with air feeds out of 'T' fittings, and 1/4 turn valves at the bottom to release trapped moisture. At critical feeds, such as for air for spray guns, an air filter like this: http://www.northerntool.com/shop/tools/product_200349692_200349692?cm_mmc=Google-pla-_-Air%20Compressors-_-Air%20Compressor%20Accessories-_-406720&ci_src=17588969&ci_sku=406720&gclid=CLyB3cmj7rgCFbCDQgodKWwA4Q
adds the next line of defense from contamination. Being sure to never use spray air hoses to deliver air from unfiltered, 'dirty' sources ( straight out of your compressor) is important, and using inline gun filters. In my experience, the vertical pipe right off the compressor traps a lot of moisture.

If you take none of these precautions, just using an air line straight off the compressor, you can almost be assured of moisture in your air at some point or another.

I have not had blush problems from spraying unthinned lacquer with Cardinal, or other lacquers (only did that at first to 'learn' Cardinal in my environment/ tools, I always thin it now) I do not need to use retarder either. I do not live in what would be considered a humid environment. It is possible your gun/ spraying technique/ settings would work without thinning, but thinning will almost certainly give you a better finish. Unthinned Cardinal could cause you a lot of headache trying to get it 'flat'.

It is easy to get thinner to spray 'what looks correct', you need to set the gun for the exact lacquer mix you are spraying, and most likely check it every time unless you are doing a lot of production and just pumping finish through the gun. You cannot really see much of value by looking at how thinner sprays, maybe just to check if there are major clogs in various places in the gun, which there should be none.

Michael Smith
08-08-2013, 07:18 AM
My bet would be moisture from your compressor if you are not filtering the air with a moisture trap. You can get one from Harbor Freight for $40 or $50 that works fine. I have been using one for many years. It follows my harbor freight rule of not purchasing anything from harbor with moving parts. I thin Cardinal as others do but I don't get blush if I don't but in my part of the world humidity is usually under 45%.

08-11-2013, 06:03 AM
Thanks to everyone for the advice. I did have a cheap inline filter so I think my issue was that it was just too humid and I was too aggressive in laying down coats.

Durring the week I sprayed the finish with some very light coats of just thinner to rewet the surface and release the moisture and had good results. I then wet sanded it with 300 and used naptha to check if any blush was still noticeable.

Yesterday we had a nice dry day in new england so I setup my fans and lights and gave it another shot. Per Chucks recommendation I reduced 5% and did many more thin coats then I did before.

I think at this point I am going to wait a week, sand to 1000g and buff.

Thanks again for the help.

08-11-2013, 08:15 AM
50% to 100% reduction (100% reduction being 1 part lacquer to 1 part thinner) would probably give you better results than 5% reduction. In my gear, Cardinal, and almost every other lacquer I have sprayed, 5% is nowhere near where I reduce it to. 'many' coats of 5% reduced Cardinal would give a pretty thick finish if they are sprayed correctly. As each coat goes on, you really want it to be laying out glassy smooth, fully wet, not granular to sight or feel. Reduce until it lays out right, and spray fully wet coats.

If you are really ready to cut and polish your ukes, meaning they have been sanded to 'dead' flat everywhere, at least once, with no voids, personally, I would start sanding at 1000 grit with rubber and foam blocks, with a spray bottle of water with a couple drops of dish soap to act as a wetting agent. If you start with a coarser grit, you are likely to sand through or to leave scratches that can be difficult to see until you start to polish, and may cause you to sand through in removing them. 1000 grit cuts plenty fast anyway. After 1000, the Abralon or Trizact abrasives work really well for pre polish, used on an orbital sander with the soapy water. You can start with 3000 grit Abralon and check progress frequently by wiping with a clean soft towel. Look for sanding scratches left by the 1000 grit. When it is looking dead smooth, time to buff with polishing compounds.

Good luck!

Moore Bettah Ukuleles
08-11-2013, 09:18 AM
I had suggested up to 5% retarder in addition to the usual thinning. My mix for my HVLP setup is 60% lacquer/ 40% thinner plus the retarder.

Rick Turner
08-14-2013, 04:36 PM
Cardinal calls their retarder "co-solvent".

And many coats means how many? Spraying "many coats" in one day is NOT a good idea. Three coats maximum, and those pretty thinned out as per previous suggestions. If you lay too much on, it will skin over "dry" but it will take forever to cure underneath. One trick with lacquer undercoats is to scuff sand them the next day with 320 and cut through the surface. It will dry faster.

Finishing will take up a good 1/3 of your labor hours finishing an instrument...if you want pro results.