|Home » Forums » Professional Finishing » Message||Login|
You are not logged in. Consider these WOODWEB Member advantages:
Micro bubbles/pinholes - Kremlin System4/11
We are having issues recently with our white lacquer for which we have a very odd situation.
We are spraying ML Campbell Resistance White, 10% Care Reducer, 10% Catalyst. sprayed with a Kremlin EOS 15-C25 (15:1) pump system.
09114 solvent based tip (have also tried the 09112 water based tip).
Air pressure is set at 18 psi, fluid pressure 50 on the pump.
When we spray, we are getting very very minute micro bubbles (almost looks as though we sprayed over a very very fine sandpaper). the kicker is, when we turn off the fan on our spray booth and spary a sample we get a near perfect finish but I cannot understand the correlation to the finish with the spray booth on versus off, and it's impact???? We have a make-up air unit that is interlocked with the spray booth supplying fresh outside air to the shop (the make up air unit is a contained unit with filters and propane fired heating element). Is it the air movement? the cooling effect of moving air? evaporating too fast? fresh air supply cooler than space temp causing cooling effect at surface?
the link between your fan being off and the finish surface being better is that you have no air movement thats forcing the surface to dry faster and entraping air/solvent. You need to retard the material a bit to slow down the dry time to allow the solvent and/or air to escape.
its been well over a decade since ive used ml campbell products so i cant remember what we used as retarder with the resistant.. but with my sherwin williams conversion varnish i use 3%-6% max EEP to retard. And depending on the weather conditions, if the eep isnt giving me satisfactory results i use naptha 150
from their data sheet:
Resistant Catalyzed Pigmented Varnish should be reduced to spray viscosity by using M.L. Campbell
Thanks, I will try this. The weird thing is this only started in January, and the only issue / change I can recall is that we had a power outage over the holiday period, which could have thrown our controls system off.
I will continue to investigate both avenues, but I have a whole bunch of doors to get sprayed so I need a solution fast.
I find the combined knowledge on this forum to be priceless and I am always looking at posts / comments on many of the forums. Thanks again!!
Please be aware that retarder stays in the coating longer than reducer. It acts as a temporary plasticizer. Be careful when you're packing and moving your finished surfaces. They might scratch and mar easily.
I could never get Resistant to work nice. Always had the bubble problem.
Then they came out with Stealth. It's a much better product for me. I rarely have any problems with it.
It needs to be thinned more than Resistant.
Usually 20% works well. I use a mixture of Reducer and Flow enhancer #2. I make a mixture that I put in a gallon can. 30 oz Reducer and 20 oz #2. Then I use that at a 20% thinning ratio.
Try Flow Enhancer # 2 first. It has worked for me in a 10-14 Kremlin and MVX gun.
We had a similar issue late winter of this year, Stealth and magnamax and nobody could diagnose it for sure. We tried tips, fluid and air settings, a couple of other brands and processes. I changed a belt on our rooftop make up air that I noticed had started to squeal and the pin holes stopped. Prior to that, we had tried wetting the floor, playing with temps, heating the cans on a heating pad, thinners, retarders, reducers, even covering the booth filters partially in an attempt to slow airflow over parts. We kept daily logs of humidity and temperature looking for a cause with no variation. What we think is that the warm air make up unit was not keeping up and we were pulling cooler air via the shop as well as contaminants from not having the positive air pressure designed into the system.
we started out with oil contaminant in our air lines and the fish eye from a new filter being added. finally got all the gunk out of the lines and back to sparing good finish...for about two weeks....then we get the micro bubble issues. Tried the stealth as above but we could not source the flow enhancer #2 locally so our results weren't great. i did some quick checks and we are pulling about 60 fpm of air through our booth and it is flash drying the surface.We are now adding a VFD to the fan to slow down the air flow at the booth to see if we can find the right balance point. will let you know how it turns out....
Here is a little cheat sheet from Campbell
I either use a 06-114 (36-511) for just about everything that isn't a large surface.
Or an 09-134 (36-613) for large surfaces or when I'm in a rush.
I'm interested in a 12-174 (36-815) for large surfaces, but not sure if the 10:14 pump can keep up with the .015 orifice.
Clears I do 35 PSI liquid and 16 PSI air
For a small fan using the 06-114 tip I do 20 PSI liquid and 27 PSI air with the knob on the gun cranked for the smallest fan pattern. I use this for the initial spraying of the bevel on MDF panels.