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Fading spots in water-based poly finish3/29
I'm running into a problem with light-colored fading spots using Minwax Helmsman water-based poly in Gloss.
I'm finishing a Claro walnut dining table and have applied 8 coats. Re-coating and gently sanding at 320 grit to remove brush marks doesn't get rid of the problem (see picture below, which was taken after 8 coats and is sanded to 320 grit).
Hoping someone on the forum here has run into a similar problem and has some tips for rectifying this without starting from scratch.
I'm open to any and all suggestions here.
Also, to minimize causal factors, it might be worth noting that I've properly stirred the poly before application, used a Purdy Chinex brush, and I've tried a couple different sanding methods without applying pressure (block sander and random orbit at both 220 and 320 grit). I'm working in 65-70 degree temps with ~80% humidity and have waited anywhere from 24 hours to a week between poly coats.
Finally, I chose Helmsman because I wanted to have a clear, high-gloss, non-yellowing finish that could expand/contract a bit and withstand abuse and UV. Ultimately, I intend to polish and buff to a high gloss after wet sanding with something like Micro-mesh. Thus far I'm not terribly impressed with this Minwax product and am considering something from General Finishes (e.g. the EF High Performance Polyurethane Top Coat-Gloss). Suggestions on a water-based poly would also be welcomed.
I have no idea what's causing your problem. You should not need to apply 8 brushed on coats of anything to obtain an excellent finish and I wonder if that's part of your problem. I would consider stripping it off and starting over. I know that sounds painful, but sometimes it's the best option.
If you decide to change product, however, I recommend you consider GF's Enduro Clear Poly if you can spray, and their EnduroVar if you can't. I really like the High Perf. Poly, and it does have an excellent UV package, but it is not nearly as chemically durable as the other two, and I would not use it on a dining room table.
If you do decide to start over, I recommend you consider a wiping the walnut with a very light coat of BLO, then seal that with dewaxed shellac, followed by the WB topcoat. As much as I hate BLO most of the time, it really brings out the beauty of walnut. This is BLO + shellac + GF HP Poly on walnut veneer.
Thanks, John. At this point it's not a complete deal-breaker to strip the poly and start over, as I only have ~4 coats remaining after multiple attempts to correct the issue (I've sanded down with 150 grit a few times to determine if the issue was from previous coats, but that wasn't the case since the spots appeared in different places each time).
Incidentally, I recently spoke with some folks at Rockler and they noted that the GF Enduro poly would amber a bit (something I'm trying to avoid), so I may explore your suggested BLO route -- provided I strip everything to the wood -- and apply several coats of GF's High Perf. poly on top.
I'm not a finisher, so I've got a couple follow-up questions...
1. Is a dewaxed shellac necessary between BLO and WB poly?
2. Any particular reason why you'd suggest not using GF's High Performance poly on a dining table?
3. Am I correct assuming that BLO won't amber once it's penetrated, and WB poly won't have an issue being applied over BLO or shellac?
By the way, stunning finish on that walnut veneer.
In my experience, waterborne poly looks terrible on walnut, I have had the same sort of problem with GF's waterborne clear poly. I have used lots of GF clear poly on maple and it doesn't amber at all, at least nothing like a solvent-based lacquer. I switched to their Enduro-Var for walnut and cherry and it looks really fabulous. Yes it starts out with an amber tint but it gives walnut that deep glow that you want.