I haven't run into this before, but on a recent kitchen, (last fall), I sprayed pigmented Kem Aqua Plus over their recommended sealer. I just had a callback and there appears to be a couple small spots that flaked off, maybe 1/2 - 3/4" long at the beaded face frame area. I don't know if sanding too fine might have been an issue or bad primer or what. Wood is hard maple sanded to 220. Anyone had issues with this finish bonding well? Bare wood shows so the primer seems to not have hung on. It also doesn't appear to be a customer damage thing.
"Wood Finishing System
1. Primer—apply Sher-Wood Kem Aqua
Plus Surfacer at 4-5 mils wet. Air dry
thoroughly. Sand with 240 grit sand-
paper. A second coat of primer may be
applied for improved holdout. Sand
between primer coats and before top-
2. Topcoat—apply Sher-Wood Kem Aqua
Plus White at 3-4 mils wet. A second
coat may be applied. Sand with 240
grit sandpaper between coats.
3. A coat of Kem Aqua Plus Clears can
be used a final coat for added perform-
4. Dry—allow overnight drying before
stacking or packing
5. Maximum dry film thickness of the
system should not exceed 4 mils. "
Thanks for the input guys. I think I followed the correct procedures from what I have read on the Kem Aqua site. It really seems as if it's a primer issue as where the finish is off it's right down to bare wood. I've used BIN's alcohol based primer before under other waterbourne finishes with no problem but in this case used SW primer they recommended.
imo sanding maple to 220 grit is way to fine for raw wood sanding for waterborne or solvent coatings. If an operator by machine, random orbit or by hand is over using their paper, then you have potential to be sanding to a final smoothness of 320+ aluminum oxide abrasives we typically sand with for raw wood are designed to dull their cutting points as it's abraded, thus leaving a finer finish when the abrasive has reached it's pinnacle. silicon carbide grain is designed to fracture under pressure always leaving a sharp cutting edge to the grain structure and that's why we use silicon carbide to sand sealer or finish... so it cuts well and leave a consistent depth of scratch. IMO for first initial coats on any species for maximum adhesion 150-180 grit is the maximum.....
I've used WB for almost 15yrs and I think 220 especially on hard maple is not the way to go. The possibility of burnishing is definitely in play.
You say it's on a beaded face frame? Not the doors? It's possible A. minor contamination before sealing. B. wood movement with moisture from normal kitchen usage. If your issue is near the sink or dishwasher(think steam) areas wood movement allowing moisture into and under the finish could be the culprit.
My opinion differs; when using a WB primer on bare wood (something I avoid if at all possible) 220 grit white wood sanding should be fine all that h2o and possibly the water soluble solvents in the primer are still going to swell the wood which should give you plenty of profile for your primer to hold onto.
As to why you have some lifting/peeling; I'm guessing you're getting some moisture in behind your finish resulting in some swelling and shrinking. Kem-Aqua dries hard and has very little flex, it just takes a just a couple of swell/shrink cycles and it will start to pop.
Using the pigmented primers I don't see a downside to sanding the wood with 150. The primer fills well enough to hide any scratches in the wood. I would not use 150 to sand the primer I use 280 to 320 for that. We use one heavy coat of primer sanded back very well with a lighter coat on that scratch sanded before the topcoat.
Of course the peeling could be completely unrelated to the white wood sanding.
Thanks again for all the info. I do think I may go to maybe 180 for my final sand of the bare maple next time. If there was a moisture issue in the wood it seems as if the failure would be between the more flexible primer and the finish coats but I'm not sure, just guessing. One spot was near a sink but the other is not. One issue I have noticed with sinks is the farmhouse sinks that are not wiped down after using them. Water on the top front edge runs down the face and right onto the cabinets, unlike a drop in with an overhanging countertop. Might be a long term issue for finishes there.
Most of my experience is with MLC products. Their Agualente primer(and the Polystar before it-17yrs ago) is one of my favorite products. It goes on thick while leveling out perfectly. The can feels like a bucket of sheetrock compound. It sands like auto primer. No grain raise.
I've used buckets of BIN as well. The BIN sands harder, clogs the paper, and raises the grain more. Its more like sanding sealer. Not as good a coverage because its so thin. It also clogs the tips frequently.
We frequently do primed only work. The customers often thin the cabinets are done, because we lay on a heavy coat of primer then lightly sand it with 240.
Our schedule for all products is 150 grit wood, primer, 240 grit, 1st topcoat, 320 grit, 2nd topcoat.
Primer needs the scratch pattern to promote adhesion (give it something to bite). Any primer worth a damn will contain enough solids to fill the measly 150 scratch.. if it doesnt, find a better primer.
"I think I followed the correct procedures from what I have read on the Kem Aqua site. It really seems as if it's a primer issue as where the finish is off it's right down to bare wood."
you have clearly not followed the correct procedure. If your primer is falling off the wood completely your preparation is to blame. you need to promote the adhesion, not polish the wood. I never sand substrate past 150 before primer. The only time ive ever had adhesion issues was when i worked for a company in my early years that prepped their maple to 220 before primer. We would often see finish flaking off to bare wood and the finishers would blame the primer.
When i began to have a much better understanding of the limitations of coatings and how to properly prepare bare wood i have had no issues. So you can go ahead and prep it to 180 if it makes you feel better, but may i ask you what you have to gain by sanding with a higher grit? I mean 150 would obviously level your surface and remove defects faster, and will also give a deeper scratch pattern/promote adhesion.
Not sure how old this thread is but any help is greatly appreciated. I got flaking on C Aqua Plus white and the C Aqua primer in tight on some detail work where I did not get all of the hide glue cleaned out.
After better detailing that problem was resolved.
Two questions. If I use Bondo to fill a table top, which I have never used, is that compatible with Chem Aqua Plus White ? Am I wrong to use a non water soluble filler since it is a water based lacquer?
Ok, three questions. Despite using 150 grit on raw wood and the recommended 220 on raw wood I still get the scratch pattern coming through on the first and second coats of the CA Plus White. I also sanded between primer and lacquer coats as recommended, Suggestions please as I have to get this project done.
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