Question
I have a few questions about lacquers and spray systems that I am using at work (a small construction company). I am the only journeyman cabinetmaker in the company, so everyone relies on me to get the finishes right. I primarily spray new wood, stained or bare, mostly oak/maple/alder.
We have a dedicated spray room, and inside the room is a spray booth, with an exchange air system and a heat toggle (can't adjust the temp with the heat turned on, but it feels like it keeps the room around 20-30 degrees Celsius). Overspray isn't an issue for me with our room setup.
The only spray system we have currently is a Graco HVLP 2500 turbine along with the Graco HVLP cup gun. I have only been spraying lacquer for about 2 years. It's pretty much been trial and error to get a good looking finish.
The lacquer I use is Cloverdale Excel Plus (pre-cat, 25/40/60 degree sheens), thinned anywhere from 5 to 40% with Cloverdale Clovathinner #19. This is the only lacquer I've tried, as it's readily available.
I can get an awesome looking finish. The problem is, every piece I spray has very poor adhesion and scratches very easily. I feel bad taking anything out of the booth that looks so good, but has basically 0 resistance to scratches/scuffs. Even after the pieces have dried over a week, if you scratch them with a fingernail to make sure they have cured, they scuff easily, and the lacquer chips off if you scratch it in the same spot a few times. It seems like it's taking it off right down to the stained/bare wood.
I use the lacquer as a self-sealer. My first coast is fairly light so it doesn't take a lot to sand (oak/maple/alder), and I usually put on 3 topcoats after the sealer to get it looking how I want. I generally sand after 20-30 minutes for my seal coat, and try to leave every other coat at least 1 full hour before I sand/recoat.
I have done a lot of testing lately with the HVLP gun and different thinning amounts to see if I can get any different results, but it just seems like it's doing it no matter how I spray it. Cloverdale suggests only thinning the Excel lacquer to 5% max, so I tried that a number of times, and even though it has trouble spraying through the tip (#3 fluid tip/needle) with such a low powered turbine, it doesn't orange peel, I just have to spray a lot slower. When I thin it around 20-30% I get the easiest spraying, but the results are still the same.
I have tried all the settings for the air adjustment on the gun, from max to the lowest I could get while still being able to spray a proper spray pattern. At each of those settings I have also tried different amounts of thinning from 5 to 40%, yet it still scratches and has very poor adhesion.
The fluid I have set to max, which isn't a lot for the gun - I just have the trigger wide-open and adjust the air as needed. My topcoats are applied around 5-6 wet mils. Has anyone had experience with finishing problems like this? I really want to produce the best finish that I can get with my current spray system. Upgrading our system to a pressure pot or air-assisted airless is still a ways away.
Forum Responses
(Finishing Forum)
From contributor R:
If doing more than 2 coats, I recommend using multiple sealer coats, and only a final finish with lacquer. Each coat will sand easier, and the finish coat seems to dry smoother and more even when applied over sanding sealer. Also, if you accidentally get a run, it will sand out easier during a sealer coat.
Will I need to thin the Magnamax at all, and what air/fluid setting should I be looking at? I have been leaving the gun wide open to get as much material out as possible with the small turbine, and like I mentioned before, usually try to spray 5-6 wet mils. The only real setting I have been playing with is the air.
Looking up the specs of the Graco 2500, it has an output of 58 cfm, 5 psi. It's their lowest model and is only a 2 stage turbine, it doesn't have a built in compressor like the larger models, and is said to be used for "light materials such as stains, clear finishes, and light paints."
I have been experiencing this problem for quite a while, but never really looked into it and just figured it was normal. I will test a piece tomorrow without stain; I never even thought to test that. Our spray booth/room when the fan is on stays a nice warm temp - I'm fairly certain at least 25 degrees but not over 30. I will look for a thermometer to check.
On another topic, I was looking at ML Campbell's website and noticed another pre-cat product called MagnaKlear - some type of conversion varnish? I've never really understood what a conversion product is and what the advantages/disadvantages are over lacquer. I should be looking at this for kitchen cabinet doors, or just stick with lacquer?
Also, I got the go-ahead from my boss to start looking/researching a pressure pot/conventional system that I assume a lot of people use. It's a lot cheaper than an air-assisted airless setup, and can at least hook it up to a regulator/filter and have a bigger pot instead of filling the cup gun 100 times, and the added agility of a gun with no cup. Was looking at a Lemmer system, but is there a better system for moderate use?
We want to eventually convert to water-based finishes, probably within the year, and want to make sure the system we buy will be good for both lacquer and water-based.
