Alternating Between Waterborne and Solventborne Finishes

Advice on running different finish types through the same gun, and comments on the durability of water-based clears in exterior applications. March 9, 2006

Inspired by the "Green Finish" thread a while back, I decided to try Sayerlack water base for exterior doors to replace Sikkens, our current door finish. Sprayed some samples using a gravity gun and like the product. Going to test in the weather for a while before we use it on a door. The last 2 steps of the material are pretty thick, and I had to thin quite a bit for the gravity gun. I would like to spray some samples with our Kremlin.

The Kremlin has never seen water base. Any cleanup tips for this? Do I need to use warm water? We also spray pre-cat, and I wonder if it is bad to use the same system for both type finishes. Just don’t want to turn the Kremlin green. Also, if anyone else has tried Sayerlack, I would like to hear their impression.

Forum Responses
(Finishing Forum)
From contributor M:
Issue One: I have tried many times to run WB through my 10-14 and it does not work well. I get a lot of air entrapment, micro bubbling and striping at the ends of the spray pattern. I have warmed the material, thinned and retarded with no luck. I just go back to my gravity in order to get an acceptable finish. The line clearing is the other major problem. When you clean your line from solvent to waterbase, any interaction will cause a gorilla snot mess in your line filter, gun filter and in the ball gate valve. Try blowing air into the fluid pickup to purge all solvent from the system.

Issue Two: I have not used the Sayerlack product. But I have tried more than my share of WB exteriors and all seem to have decent film surface quality durability. Where they fail is in their UV filtration ability. Stains and wood will fade through the finish. How can the use of these materials be "green" when you end up prematurely stripping off the material (MC stripper is 100% VOC) in a year or two? Let's do the math… WB exterior at 275 gr/l, Isocyanate exterior at 550 gr/l, the life of the iso is between 4 to 10 years and the WB is between 1 to 3 years. As you can tell, I have stripped more that my share of WB finish (and it is not fun). Who knows - maybe Sayerlack has something different?

From the original questioner:
Thanks for the response and glad I did not put the WB in the Kremlin. Is there another system that will shoot the thick WB finishes?

I got the WB material direct from Arch Coatings. They are trying to start with WB lacquer and do not have all the exterior coatings (or knowledge) at this time. Sayerlack has several different types for exterior depending on wood types. My cousin in Italy uses Sayerlack in his window shop. He shoots everything off an overhead chain conveyer and says the Sayerlack has good vertical hold. I do not know if he uses the WB or solvent type. The Sayerlack info says to get good UV protection the colored topcoats have to be used. So it is like Sikkens and not transparent.

I agree with you about “green.” If a solvent finish lasts twice as long, that is going to be better for the environment. Mahogany is the bad boy right now with environmentalists. But if a door or window lasts 50 years or more compared to an approved wood that only goes 20 years, what is the best for the environment? Especially when you figure all the transportation and energy used.

My concern is with a healthy environment in the shop. We have all the safety gear including a fresh air mask, but still the off gassing and material handling leaves everyone exposed. Sikkens makes my eyes water as soon as the can is opened, and that can’t be good long term. Same for pre-cat and conversion varnish. Europe has a lot more exterior finishes available than we do. Even Sikkens has WB finishes over there.

From contributor D:
I would not run WB in a solvent base Kremlin. I finish and refinish about 50 high end doors and frames a year. There is nothing worse, for your schedule and your rep, then to get a call that the door you did two years ago "doesn't look that great." You have to explain to the customer that exterior clear finishes don't last that long. I have tried and tested dozens of exterior clears, and sometimes have put them on customers' doors without testing them. I have tested 3 to 4 WB exterior clears and have never seen one last two years in heavy sunlight. I try to test with frame and panel con. because that's what you are finishing. Sunlight is the killer of exterior finish. Do tests! Refinishing your own work sucks.

From contributor M:
I normally shoot WB with a gravity gun - it cleans out better.

Contributor D, we finish about the same amount of exterior units a year and about the same refinishes. It is always nice to know what anyone else is using. Please do not tell me you are using spar or Home Depot poly.

From contributor P:
I run waterbase (Becker, Fuhr and Target) as well as solvent (Becker & MLC) through my 10-14 with no problems. After WB, flush thoroughly with water, then denatured alcohol, then lacquer thinner. Reverse the process when switching to solvent based. If the gun is not being used for more than 24 hours, I leave lacquer thinners in the lines. Before starting up again, I run thinners for a couple minutes, then check the screen at the base of the gun, getting rid of any crud that may have accumulated there. The air cap and nozzle go into a jar of thinners after each use. It's been working well for about three years.

From contributor B:
It is okay to use any AAA with water-based products, so long as you keep your fluid lines and filters clean, especially if you plan on switching off between WB's and solvent-based finishes. Before I made the complete changeover to WB products, I would run the related solvent through my pump to clear out any finish, then I would follow up with denatured alcohol before proceeding. Water-based finishes = warm water then DNA. Solvent-based = lacquer thinner then DNA. I never had a problem as long as I made sure the pump and fluid line where cleaned. I soak my tip set in a sealed jar of acetone and then blow it clean/dry before using it.

As for AAA pumps shearing water-based finishes, you need to run a test. Not all WB's are as shear sensitive as they used to be, but there are still a few brands out there that can be shear sensitive. Talk to the manufacturer of the coating and get their guidance. Try it - you'll like it...

From contributor D:
No polys or spars - I use ICA exterior 2k urethanes. My big problem is I use Mohawk stains and they fade. Red fades quickly. ICA makes a non-fade waterbased exterior stain, but I have had no luck with the application process.

From contributor K:
There are many users spraying waterbased coatings with the Airmix system. Some do have air entrapment, but this can be caused by many things including having the atomization air turned up too high. Kremlin does have a new tip called the xtra tip for spraying waterbased coatings, high solids coatings and polyurethanes. This has tested out well and is available through all Kremlin distributors. If you are having trouble spraying your coatings, you may want to try this tip. Current users love it compared to the regular tips for the coatings I mentioned.

From the original questioner:
Thanks for all the good info! I will continue in my quest for "green."

From contributor A:
Always interesting when talking 'green' finishes. I have used Compliant Spray Systems Enduro Poly several times for exterior doors, one approximately 4 years ago and have not heard a peep about it. Based on other responses, I should have refinished it twice. Some finishes are better than others, just like the solvent based. I have heard great reports of the Target and Fuhr products and am looking to switch to one of those. By the way, I've seen spar varnish delam in several years if exposed to harsh environs as well.

As for equipment, I have used an HVLP and now the more efficient LVLP version of HVLP. No problems other than operator error in settings. I have had problems with oils, solvents and such getting on the wood prior to finishing. I suggest that you purge your shop of all silicone based sprays for your machine tables and such. Silicone will wreak havoc with water based.