Compressor or Turbine for Spraying on Site?

      Which air setup (and which gun) is best for on-site finishing? November 25, 2008

Question
I run a two-man shop and do a great deal of onsite refinishing. Up to now I have been using HVLP with a portable compressor. I am thinking of switching to turbine. I go through about 30 gallons of lacquer per month and approximately 50% of that is onsite. I am using Oxford, Enduro, and Durolak, all water based. If you were in my shoes, what would you do - continue using a compressor or switch to turbine?

Forum Responses
(Finishing Forum)
From contributor P:
I wouldn't want to lug a compressor around myself. Most HVLP guns take a lot of CFM to spray properly, which means a pretty big compressor. I have a Turbinaire turbine setup that's been a real workhorse for five years. I've switched over to AAA for most of my spraying, but I still use the turbine for shooting stains, sealers, etc. I shoot mostly waterborne, too.



From contributor M:
Before you buy the turbine, check with your finish manufacturer. I know that ML Campbell does not recommend that folks use turbine sprayers with their products (especially the post cats) because of the heat that the turbine air carries. I can't say for sure because I've not used the turbines much myself. I have several friends that use turbines and spray pre-cat, and get fantastic results. If the manufacturer says that turbines are fine, I would not hesitate to buy one.


From contributor A:
I believe ML Campbell also recommends sanding between every coat with 240 grit paper. This will increase adhesion to the point that there should never be adhesion issues. The only obvious problem is you can see 240 grit scratches.

Just because the manufacturer says something, it often has more to do with their own liability than the real world.



From contributor D:
Turbines are turbines, but in my experience the only turbine gun worth a damn is the Accuspray 10. With this you can get as good of a finish as any gun on the market.


From contributor M:
Well, I've been using 220 grit for years with their products and only have problems if I am trying to sand too quickly and getting lacquer corns on the sandpaper. I've used Mirka Fineflex sandpaper and it works just fine. I've used 3M's fine sanding sponges, which feel to me to be a good bit more coarse than 220, and don't see sanding scratches. I only spray pre-cat and conversion varnish.

I do understand your point - manufacturers usually give hit-n-miss advice, but sometimes that's all you have.



From contributor A:
Contributor M, you have never sprayed paint.


From contributor D:
Contributor A, on this I must disagree. I have no idea as to whether contributor M has ever sprayed paint or not, but I've sprayed enough to fill my in-ground swimming pool and I sand between coats after sealer or self sealing, prior to first topcoat, with P240 all the time without issue using pre-cat, C-V or 2K urethanes. There are a bunch of variables here. A random orbit sander produces a scratch with P240 that's finer than the scratch produced by P400 used by hand in a straight line because of the self-canceling scratch pattern this type of machine produces. With sanding sponges, the rule of thumb is 3X standard sandpaper due to the flexible backing. I used P150 sanding sponges and according to Dixon Industries, the provider of this product to just about all sanding sponge retailers which they then go on to private label, this is equivalent to about P320 sandpaper. This is because of the soft backing which greatly affects the scratch. Valspar, my preferred wood finish supplier since its good stuff and I can buy it cheap, also recommends P240-P280 for between coat sanding, so it's not just MLC. I think you're off base here.


From contributor A:
I had no idea that there is so much variation based upon substrate. As you mentioned, I was referring to a sheet of 240 paper. I'm aware that 320 scotch brite pads leave less scratches than 320 paper. I retract my prior statement. This is an apples and oranges situation.


From contributor N:
Regarding turbine setups, whatever you end up with, I think the most important consideration is that the gun is a non-bleeder. The Accuspray is a nice gun because it does a superb atomizing job. Many of the guns do a great job and so much is dependant on the operator rather than the gun. But the Accuspray turbine gun usually gets the most rave reviews, as you can see from contributor D's enthusiastic endorsement. I have Accuspray and Croix/Graco/American Turbine guns. I've used the Wagner (a great gun) and the Titan (a good gun but the trigger is way too stiff and does cause spraying fatigue in the hand).

Regarding the need to sand when using MLC pre and post catalyzed materials, the reason for this is simple. The possible chemical bond between coats is not reliable enough, so the formulators want to see a good mechanical bond to insure proper intercoat adhesion.

The lacquer thinner that MLC makes is designed to be weak in terms of its solvency, so as not to introduce recoat windows with their products (that's how they do it, making materials that have virtually no recoat windows). It's the solvent strength of a finish that makes for a chemical bite between one coat and another.

The MLC lacquer thinner is a balanced blend of liquids designed to compliment and work with the MLC coatings to get the best possible flow out and cure times for each of the coatings which the thinner is recommended (according to each coating's tech sheets).



From contributor L:
I use compressed air in our shop and lug a small compressor to job sites when necessary, but a friend of mine uses an airless and absolutely loves it. When he helps out around our shop in a pinch, he always brags about his airless. He can really lay down a sheet of glass. We both spray about the same in technique and usually our final outcome is very consistent. We have AOM guns that are in top shape, so we aren't going to make the jump.

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