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Agualente primer revisited10/5
I posted last year about a problem I was having with the mlc agualente primer, which is that when spraying through my airless (titan 44i) I get random cratering across the surface, especially on large surfaces. It seemed to become less severe when I switched to using 5gal pails instead of single gallons, for a while. Then in the last couple of months it has been just as profuse as before. I have contacted MLC and they were not helpful, stating that since there are too many variables for them to be able to give me any advice. The occurrence is completely random as far as I can tell. It doesnt seem to be contamination of any kind nor is it temperature related. No other waterbased products do this through this spray system, only the mlc primer. General finishes primer doesnt do it, but it is not stain blocking, and their stain blocking primer is way too expensive for me to be competitive with it. Chemcraft wb primer does not do it, but has a long term weakness to moisture in my testing. Valspar zenith primer does not do it, but it doesnt flow out as well, and causes the top coat to have a lower sheen than the other primers...Other than the cratering the mlc primer gives the all around best result. It lays out like glass when sprayed through the airless, other than the random cratering. My only thought is that the primer is not designed to handle the high pressure of the airless system, because when I do small tests with my gravity gun I do not get the cratering problem, but it also doesn't lay out as smooth. I like the primer a lot and it has many good qualities, but this random cratering is a total killer and causes me to have to sand more aggressively and a times shoot an extra top coat. I dont really have the money to upgrade to a nice AAA system, unless someone here has a used one they want to sell me ;)
... Is anyone getting really nice atomization and flatness of finish with any particular pressure pot set up? I would like to switch to something like this as it would also reduce overspray and increase material savings but I dont want to take a step backwards as far as finish quality. right now my end result is almost as smooth as glass, other than the damn cratering.
If you are putting it on too heavy, which is easy to do with your set up, it could be causing surface tension, which in turn could cause the cratering
I feel like Im doing just enough to lay down a nice wet coat that flows out. Any less and I would have orange-peel problems. Im using a 312 fine finish tip, and I have tried a 308,410, and 314. All with similar results. I do however think that you may be on to something with the surface tension issue, I just dont know how to solve it other than to switch to a different rig?
Try a little more reduction of the primer?
We played with the Agualente for a while and had the cratering you described. It was caused by surface tension. Thinning the product with about 5% methyl hydrate eliminated the problem as it served to reduce the surface tension.
I suspect any alcohol would work, methyl hydrate, denatured, vodka....
A little OT. Has anyone tried Zinnsers WB stain blocker? I've been using the shellac based under GF WB for awhile but it's getting pricey as well.
If you need atainblocking then use shellac, it works better. Otherwise the wb works like a traditional primer
Thanks JM. I Finaly got a hold of the local MLC rep and he said exactly the same thing but to use their brand of flow additive at about 3%. I have yet to try it, but i hope it works. About the Zinnser shellac under the GF, Idid this for a while but discovered some long term durability issues. And as for the Zinnser waterbased, I just didnt think it dried and sanded well enough to want to add it to my system. Im hoping that thinning it with their aquastar flow additive will do the trick, otherwise it looks like im going to have to keep shopping for the right primer, or start shopping for a new spray rig that will handle the primer better
Update: Thinning with alcohol has no positive effect on the cratering.
The Final attempt will be the aquastar flow additive as recommend by the MLC rep. If this doesnt work then I will have to give up trying to get this primer to work through my airless system
Final update!!! the aquastar flow additive did nothing. I also tried a couple of different sizes of the new low pressure tips from graco, which by the way are pretty nice, but to no avail. After this next job has shipped I think I will be switching to the valspar zenith primer, even though its a little thinner and doesn't sand as easily. At least I wont have moon craters in an otherwise perfect coat
Jonathon just what are your issues with Bin shellac? I've been using it with no water issues at all. I put it down first. Sand/caulk and then seal with GF white undercoat. Sand and seal with GF sanding sealer. Then two topcoats of pigmented poly.
I have three issues with the BIN Primer
1. It does not clean up with soap and water which requires extra steps when going back and forth with GF products
2. It does not sand as well as the GF, MLC, or chemcraft primer
3. I was using the Tinted poly directly over the top of it and in this instance I seemed to have some compatibility/ durability issues over the long term(over the 1 year mark) with the 3 wb primers listed above the poly seems to dig/bite into it much better this is ultimately the reason I quit using it. but I did not try using the GF undercoat as the second primer coat as you are doing. I thought of it but again for me it was just too much switching between products