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Micro bubble hell11/10
I've been using Target EM9300 for a few months now. At first, it was spraying flawlessly. Really nice looking finish on my signs. About 2 weeks ago, things took a turn for the worse, and I cannot for the life of me figure it out. The first coat sprays on nice and clear. The second coat, as it dries, develops a surface that looks like a thousand little bubbles that are cut in half. Like if you took a sphere and cut it in half and peppered them all around the surface of the sign. I spray with a Fuji 5 stage turbine. I've tried 1.3, 1.5, 1.8, and even 2 mm tips. I've tried rinsing sanding residue between coats with distilled water, thinking that maybe my water has developed some kind of contaminate. I've cleaned my turbine out and flushed the hose out with water thinking that maybe there was dust in there, I've tried playing around with the temperature and humidity levels in the drying room. Nothing is working. The funny thing is that if I spray 5 signs all back to back, same techniques, 1 or 2 will come out great, and the others will have the terrible looking finish. Sometimes, a sign will have the bubbles in some areas, and not other areas. I'm really puzzled, and I dont know where to go next. Thanks for any help you can provide.
I was having that problem too with the EM9300 Polycarbonate. I switched guns from HVLP to air, spraying at a higher pressure with less material. Seems like it bubbles when applied too heavy.
Off topic, I was sampling out the EM 9300 for interior casement window sash on bleached white oak, letting the finish cure for a few weeks. I opted to use the 9300 for UV protection and protection against water. After doing standing water tests, the water penetrated 4 coats, causing wood to get wet beneath the finish. The 9300 turned white as well. After the water dried, the finish recovered as did the wood, without leaving a stain or blemish. How long do you wait before putting an exterior piece finished with the 9300 into service? Seems like it takes a long time to cure before it can hold out moisture, much longer than the tech sheet states. I sealed the wood with de-waxed shellac. The pH of the Polycarbonate didn’t seem to affect the shellac. I know the tech sheet specifies a minimum of 5 coats. Can you, or have you used the cross linker with this product?
Try contacting Jeff Weiss at Target. He's the owner and chemist, and sometimes answers the phone himself!
Thanks, he always answers the phone himself, at least the few times I called.
Jeff couldn’t quite give me an answer on the curing time before it will hold out moisture. I switched to the 9000 instead for the interiors of the window and door pak. It performed better with the standing water test.
I had the same micro-bubble problem with EM-9300. First coat OK, then disaster. I talked with Jeff at length more than once, even sent him photos and the gallon of mostly unused material back to him after I tried everything he recommended w/o success. He blamed it mostly on the white oak I was spraying it on. He asked that I increase the N/N size on my pressure feed HVLP conversion gun. I did, no change. Spray heavier coats (5 mil); awful. In the end, he refunded my money AND said he would send me a new gallon of product. I thanked him but asked he send some EM-6500 instead, and he did.
I switched to GF's Exterior 450 and had zero problems. I wish the EM-9300 had worked for me because it looks great (except for the bubbles) and it is much harder, sooner than the GF product. A year later, the door I used the GF product on still looks great though, so it is working.
If I ever do try the EM-9300 again, I plan to add some of GF's Extender to it. I started using it on another product that wouldn't flow out for me and it worked great. It's become my go to additive whenever I have flow out issues with WB topcoats.
Yeah I'm still in complete hell with the 9300. I thought I had a Eureka moment when I though maybe the HVLP turbine was sucking in cold fall air, so I moved it into the drying room where it's 77. I also moved the Target into that room, and keep the signs in there for an hour or 2 before I spray them. My thinking was that if it all was the same temperature, things would improve. The crazy thing is, once in a while you get a great result, but the other 5 signs you sprayed at the same exact time look like hell. So the temperature fix was a failure. So I started thinning it with distilled water...... which really stinks, because the stuff is already water thin and doesn't build... I thinned it with 5%... no good... 10%... no good... 15%... Terrible.... so, here I am back to square one after a month of this. I'm beyond frustrated. I feel like I'm going to have a stroke. I have a zillion orders to get out and I can'[t solve this problem for the life of me. I am completely willing to switch to another product that is forgiving and stable. I don't care what it costs, or if it's water based or not. I'm so desperate, I'd try anything. If anybody has any recommendations for an exterior finish that fits the bill, please share. Thank you
I've tried GF 450... sprayed nice. Great looking. Didn't care for the build to be honest. But I would live with that. My problem with it was it takes too long to get hard enough to ship. No matter what I wrapped the signs with, it would mess up the finish even after several days of sitting around. I need something that will ship faster. Target does that well. That's about the only consistant thing I can say about it.
I've made the decision to ditch the Target and go back to Sher Clear. Even though I had problems with the Sher Clear, they were minor compared to the Target. If anybody reading this is looking for an exterior WB clear, I've tried quite a few now, and SW Sher Clear is superior to the rest in many ways. First, it's thicker than the others, and I've never had to thin it to spray it, so it will hold on verticals much much easier than say Target. Of course you can overspray it and cause it to run just like any clear. Second, it builds much much faster than any of the others I've tried. 2 coats of Sher Clear is equal to 4 of Target, and I'll bet it's even more. That's just an eyeball test. With Target and GF 450, they showed every sanding scratch... Sher Clear will show no scratches with 320 grit. Third, Sher Clear is shippable the day after it's sprayed. It will not stick or distort the finish if you wrap it in shipping paper. Target was the only other WB I've found that does this as well as Sher Clear. Fourth, Sher Clear is very very forgivable. I've never had any of the problems I had with Target. The only issues that ever showed up was a finish that looked slightly dusty for lack of a better description. You could only see it under bright LED lights. I attributed this to rust in the cans in the end. The new can I just got yesterday was good. Maybe it was a bad batch a few months ago. I don't know. GF 450, Target, and MasterClear all were clearer finishes than Sher Clear. Target, when it's being nice is the best looking of the bunch. For ease of use, GF 450 and Sher Clear are pretty equal. Easy to get a good looking finish. When the EM9300 goes south, it goes SOUTH. It's the most frustrating finish I've ever used by a long shot. If you get consistant, great finishes with it, I'd love to know your secret.
Mark, your lasts couple of posts suggest that the wet film thickness with the EM-9300 was too low. Un-thinned, EM-9300 builds as well as other WB topcoats I've used, so if you are having to use a lot more coats then you must be spraying your coats too thin. Jeff always coached me to spray full wet coats, though others who know there stuff have said thin coats are best with it. I settled on 3 mils as a good target.
I had suspicions the heated air in with your turbine unit might be contributing to the problem, too, and your comments about making sure everything was warm and having even more problems is consistent with that. If you ever try EM-9300 definitely try adding GF Extender to it. That will increase the time before it sets and allow it to flow out better.
if you do want to give the 9300 another shot I would figure out a way to create a more humid environment. Spray full wet coats. and instead of thinning use the Target SA5 retarder probably around 8%.
The most interesting comments I found here were the one on the turbine heating up and the wetter build up in relation to spraying onto oak.
I'm not the pro finisher that many of the people on this forum are. However I enjoy analyzing problems like this and do have some experience with finishing.
If you still have some of the EM9300 around you can try the following tests.
1) Since the first few signs come out nicely but later ones don't I'd agree it's worth looking at the turbine. You could try letting it run for 20 to 30 minutes before spraying anything and then shoot a test sample. If it is a heat problem then you should see the bubbling on the first sample.
2) Oak is an open grained wood and subsequently air in the grain/pores can more easily escape. A warmer coat of finish will be more susceptible to allowing escaping air to pass through towards the surface of the finish, thus causing bubbling. Try some sample of a tight grained wood like maple and compare it to the oak results. You could try this both with a cooler startup air flow from the turbine and a later hotter air flow.
3) A thinner finish mixture will be more susceptible to passing air through than a thicker one. The seemingly logical solution is to spray fewer, thinner and lighter coats. However a heavier viscosity, heavier coat may be more resistant to air escaping through the finish.
Most of this is assuming the bubble are being caused by escaping air. This of course may not be the case. If it is an aging out problem with the product then it could be that a developed chemical issue makes the EM9300 less reliable with any of the conditions discussed. Obviously the only test of this is to get a fresh supply.
Tough problem. Good luck.
BH Davis, your comments make a lot of sense. Jeff at TC said that red oak was about the worst wood for giving bubbles. That would suggest you want to spray thin coats, as you said; however, he recommended just the opposite, to spray heavy coats. FWIW, I've never had any trouble with other clearcoats on red oak.
To try to get to the bottom of this I prepared some samples of EM-9300 on clear window glass. I had bubbles on all of them, whether I sprayed it on or brushed it on, thick or thin. My conclusion was that the product was bad. As I mentioned before, after I switched to GF's Exterior 450 I had no troubles on the exact door I had tried using the EM-9300 on. I had to strip it to start over, but my problems ended when I changed products.
EM-9300 has some great properties, including appearance and hardness. I would use it if the bubbles weren't an issue.
Thanks for all the help. When I was struggling with the 9300, I tried many different things. Light coats, heavy coats, moving the turbine to 3 different locations with different intake air temps, spraying test coats on different materials (cedar, oak, pvc, painted pvc, HDU, and painted HDU) and I got the bubbles on all of them. I also tried switching spraying systems to a Fuji 5 stage HVLP. After that, I tried 4 different nozzle sizes. I tried double rinsing the signs with distilled water.. The last thing I tried was thinning it 5% with distilled water, then 10%, then 15%.... It was then that I threw the target in the trash and went back to Sher Clear. It's really too bad because the Target, when it acts right is super nice looking. Water clear. But I just can't spend any more time with it.