Hi, I've got a custom cabinetry and millwork shop in Rutledge, Georgia. I have been spraying finishes for the past 24 years, off and on. The biggest problem that I have has been microbubbles popping up at different times. I have battled this problem for way too long now and am ready to figure out what is causing it and get it taken care of. I have had the issue with conversion varnishes and pre-cat lacquers. I am spraying with a Kremlin 20:25 AAA pump with a MVX gun. I'm looking for a very experienced finisher who is very familiar with my Kremlin pump who I could pay to come to my shop and help me figure the problem out. I have been around and around with paint suppliers and pump reps, as well as a plenty of tech folks. I'm wanting someone with a lot of experience actually spraying finishes with my type of setup who can come help figure the problem out. I'm located about 45 miles east of Atlanta. Thank you in advance for your help.
It's always been solvent based finishes. Years ago I sprayed a lot of m.l. Campbell finishes and had a lot of the problem happen then. Now, I'm spraying Lenmar brand and am still having the problem some.
You may have tried this already. What you are experiencing is not necessarily the equipment that you are using. More than likely the micro bubbles are from moister either in the actual air supplied to your gun or in the atmosphere. First make sure that you have a clean dry air supply. From my experience especially with ML Campbell resistant and other products in humid conditions as well as on porous woods like oak or hickory a retarder is necessary to allow the bubbles to dissipate before it flashes off. I have reasently started using Lenmar products. I have not experienced any bubbles yet. But I monitor the humidity and add retarder if needed.
Check with the mfg of the coating to make sure it is OK first but I find a couple ounces of MAK (methyl AMYL ketone) usually takes care of micro bubbles. As I recall from my short time in Georgia (and Florida) there is a lot of high heat and humidity pretty much year around. That causes the finish to skin over and then solvent causes the bubbles trying to escape through the skin. This should be even worse on open pore woods like Oak, Mahogany and Walnut. Do you measure your wet film thickness and the viscosity of your coatings? What are those measurements if you have them?
Scott, I agree that moisture is a possibility. I have a refrigerated air dryer hooked up to my air supply, but I forgot to turn it on this last time that I sprayed. But, the humidity is low and I've got 10% retarder added to the precat lacquer. Between cooler temperatures and retarder added, it seems that micro bubbles would have time to pop before skimming over. And, when I used to have the problem with resistant, I always had the refrigerated air dryer on. Also, I've got pre and post water filters inline and I've got water traps built into my air line. Those were all empty of any water. And, when I had the problem with resistant, I had tried all kinds of ratios of their Flow Enhancer #2. That is their retarder.
Rick, I've never tried MAK before. Is it a very slow retarder? Yes, Georgia does have heat and humidity issues for sure. I've got a hygrometer in my paint booth and I won't spray if the humidity is over 70%. But, I had a little issue with what appears to be microbubbles this last time that I sprayed. Temps were in the 60's and humidity was probably around 45%. Back when I had the issues with the resistant, I did check the viscosity then. But, I haven't checked mil thickness and viscosity this time. The precat is a dark pigmented lacquer that was mixed up in a water white lacquer. So, it is a thin finish right out of the can. Its not thick at all. I was spraying a chest of drawers this last time and the majority came out smooth, but there was one spot on one of the vertical sides that had what appears to be microbubbles on it. Its probably a spot about the size of a third of a dollar bill. Or, a bit larger. I also had the issue on one edge of the top that was also sprayed vertical.
Unfortunately I am located too far from you to visit. There are however some things that I would try If I were there. As Rick mentioned check your wet mil thickness. To thin and the retarder may have little or no affect. Too thick on woods like oak and hickory the film will try to bridge the open pores then when the solvent evaporates it will push up the film creating what I call solvent pops. First I would experiment with a different gun like a cup gun with the same amount of additive. If the bubbles are not present then there may be a setup issue with your pump gun. Also are you seeing the bubbles on the final coat or just the first coat? Do you get them with clears as well as pigmented? I know that I get them often on the sealer coat with clears especially if I am using them self-sealed. If you are spraying a thin film and you get the bubbles try a heaver pass. If you are spraying a heavy film try spraying a thinner one. 4 to 5 wet mils for MLC is recommended around 3 to 4 wet mils for Lenmar. 10% flow enhancer #2 should be enough for resistant but I have had to add as much as 15% to get a good finish.
From what you described it could be a spot that was missed when sanding the sealer coat or some dust that was left. As I stated in my last post if I use the top coat as the sealer then I get a lot more micro bubbles than if I use a sealer or primer this makes it more difficult to level. Also do you have an inline filter on your gun? If so check it. I know that if mine gets clogged then I will get spurts of debris in the finish. I use a cat system.
Hey Scott, thanks for your response. I almost always have used the primer that is recommended for the topcoats that I'm using. I've always primed twice (sanding in between coats) and top coated once. Unless I had problems with the microbubbles and then I would sand and recoat the part. I feel like I'm putting on the proper amount of finish. I put on a full wet coat and stop. I know if the coat is too thin that it will look and feel like its starved for finish. Its possible that there was something left on the side of the cabinet after it was sanded and blown off, but I'm not sure. I'm very particular about getting all the dust off prior to top coating. Its just so weird how this problem pops up now and then. When I was using m.l. Campbell products, I even went up to 25% of the flow enhancer #2. I think they recommended up to 20%. I was just trying everything. And back then I never did totally solve the problem. I had even been talking to a lab tech at m.l. Campbell in Canada. He sent me an additive that wasn't commercially available to add to my finish. I think he said to add .8 ounces per gallon of finish. I would say that it fixed about 80% of the problem. But, this issue keeps popping up from time to time and I am still stumped.
my kremilin is a 10-14 but had same problem with binks pot, and gravity feed guns set up also used many products from ML cambell then switched to lenmar, all CV products! trying to fix problem don't know about pre-cats i will never spray pre-cats
My Lenmar lacquer specialist stopped by today. I went over your situation with him. His first response was that the micro bubbles might be a result of not giving the previous cotes enough time to dry. He suggested the fact that it is not wide spread on the total surface and the retarders do not help this could be one of your problems. In other words if you spray on the primer coat and scuff as soon as you can then spray on the top coat. The primer coat has just skimmed over and is still trying to dry this will cause gasses to expand and push up the top coat creating the bubbles. Another comment was that the setup of your gun could indeed create this type of problem. If you have too much atomizing air then this would create the effect that you are describing. It would seem to me though that if this were the case the bubbles would be on all or at least most of the parts.
11/14 #17: Veteran Finisher's Help Wanted In G ...
Just a question first. Are you sure it is bubbles and not a spot caused by a "wink" in the spray system? I have the 10/14 pump and at times for no known reason I will get a small pulse in the spray pattern that will result in a spot similar to what you are describing. It usually happens when the pail of finish is getting low or if the temp. is cooler causing the finish to be slightly thicker.
I think you & I talked a year or so ago about something. I am located down in Washington Ga. about 1 1/2 hrs from you. Give me a call next week if you want to and maybe we can figure it out. 706/678/8645
11/17 #19: Veteran Finisher's Help Wanted In G ...
i've struggled with this for a long time and thought i would chime in with my experience.
1. my experience with mlc has been inconsistent at best. magnamax has always sprayed and layed out beautifully for me but their cv (krystal, envirovar, and klearvar) has always given me problems. i switched to 2k poly (ilva) and matador and have seen much better, more consistent results.
2. i have been told that mystery bubbles can be attributed to weird times in the seasons (specifically fall and spring). i'm not sure if i totally believe it but i have experienced something similar that wasn't ever explained as anything else (got the reps involved, etc).
3. spray with another piece of equipment to help determine if it is the product or equipment that is giving you issues. just this weekend i switched my excite gun for an older mvx and the results are night and day. i'm really not sure what my excite gun's problem is but i was getting mystery bubbles with it (not everywhere but enough to have to reshoot the finish) and nary a problem with the older mvx gun. i haven't had a chance to break it down for a good cleaning so, hopefully, that is the problem.
11/17 #20: Veteran Finisher's Help Wanted In G ...
Thanks for talking to your lenmar rep about my problem. As far as the drying of the primer is concerned, I know for sure that I always wait plenty of time for it to dry before topcoating. I always wait until at least the next day to sand the primer and topcoat. Sometimes it may be multiple days before I topcoat. I talked to a guy recently who had experienced the same problem and said that he found out that the product needed to be thinned a decent amount to help eliminate the problem. He said there is an issue with spraying m.l. Campbell's resistant with the Kremlin system.
11/17 #21: Veteran Finisher's Help Wanted In G ...
Thanks for your response. I had so many issues with the bubbles in the resistant years ago that I just finally gave up and switched to another product. I wouldn't mind using the resistant if I didn't have to deal with the micro bubble issue. I talked to a guy recently and he said that you have to thin the resistant down a decent amount to be able to eliminate the problem with spraying it with a Kremlin system. He also said to add retarder to the mix. I am currently spraying lenmar's pigmented precat lacquer. I am using the Kremlin 20:25 pump with the mvx gun. At first, I had the fluid set to 30 pounds and the air at 14. I was having a slight problem with what felt like specks in the finish. The next go round, I set my fluid to 40 pounds and kept the air at 14. The finish was a lot nicer then. I didn't notice the specks in it that time. I have tried the matador finish a good many years ago and had good results with it also.
moisture is a possability, but maby its just contaminated material,been a finisher for 20 yrs, and dont know how many times the cause has been contaminated material, and it doesnt take much of anything to contaminate a 55 gallon, a 5 gallon, or a gallon of material...it's a good possability that its coming from the manufacturer like that also, go with rudd, they are the the best, but thats just my opinion, it also could be the way youre setting up youre gun also, just a thought.
moisture is a possability, but maby its just contaminated material,been a finisher for 20 yrs, and dont know how many times the cause has been contaminated material, and it doesnt take much of anything to contaminate a 55 gallon, a 5 gallon, or a gallon of material...it's a good possability that its coming from the manufacturer like that also, go with rudd, they are the the best, but thats just my opinion, it also could be the way youre setting up youre gun also, just a thought. and it also could be what youre spraying, is the surface clean, is it vaneer, cause we all know whats under vaneer, ''glue''...is anybody spraying sillicone in the shop, that exhaust fan will suck whatever is floating in the air out in the shop rite into the spray room if the spray room isnt closed off from rest of the shop, and that can cause the finisher a whole lot of unessasary problems....
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