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Finishing My Finish... Rubbing Out & Layering Question

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Forum topic by Keith Kelly posted 01-12-2015 07:08 PM 781 views 0 times favorited 11 replies Add to Favorites Watch
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Keith Kelly

223 posts in 1131 days


01-12-2015 07:08 PM

Topic tags/keywords: question finishing

I’ve been building some walnut + cherry island countertops, and the layers are:
  1. BLO
  2. DW Shellac
  3. Arm-R-Seal Gloss (5 layers, some thinned)
  4. 1 coat of Polyurethane/MS 50/50 mix (I ran out of Arm-R-Seal due to a complication, see other thread)

There are 5 or 6 places where I applied the finish a bit too thick during the first couple of coats. I tried to sand between coats, but was pretty timid and they are still visible and raised up a bit. I’m reading the “Finishing the Finish” chapter in Flexner’s book, and it sounds like I should level the finish first with sandpaper (in a few weeks once it has cured), and then rub it out. But then he shows a picture of “layering” that happens when sanding through a coat of a finish that doesn’t fuse between coats (like mine).

Question
Should I try to fix the marks now (which is about 15 hours since the last coat), then apply another layer of Poly? Or wait until it cures and do the sandpaper-flattening before rubbing out?

I think my lack of experience is probably evident here…I’m working on a project that’s dramatically increasing my skillset, yet pushing it to its limits. Any advice/thoughts would be appreciated.

Here’s what I’m talking about:

However, most looks good:

-- Keith - Bolivar, Missouri, http://www.SquareOneWoodworks.com


11 replies so far

View pjones46's profile

pjones46

986 posts in 2111 days


#1 posted 01-12-2015 10:06 PM

One of your problems may stem back to the BLO. Polymerization (hardening) of BLO is a very slow process. It takes weeks, months, even longer and may be contributing factors to the problems with layering. However, having said that, it just may be that you did not allow enough time in between coats for drying and insufficient block sanding in between coats. From the pictures I really can not see the problem well. I would let it sit and cure/dry before doing anything.

-- Respectfully, Paul

View DIYaholic's profile

DIYaholic

19180 posts in 2143 days


#2 posted 01-12-2015 10:23 PM

Opps my bad….
Thought I had closed this thread….

-- Randy-- I may not be good...but I am slow! If good things come to those who wait.... Why is procrastination a bad thing?

View OSU55's profile

OSU55

1063 posts in 1457 days


#3 posted 01-12-2015 10:52 PM

Which coat(s) of your finish schedule did you apply too thick, #3? The arm-r-seal and poly are essentially the same. I think your conundrum is whether to keep adding poly before full cure so each coat can burn in, and not have what I call knit lines (layers that do not burn in or “knit”), and hopefully have a smooth film when finished, or let it cure more so you can sand flat now, add more poly later, but end up with knit lines.

Sorry but I can’t answer for sure. I think it would have been best to sand out when it 1st happened. I suspect if you add more poly, let cure, then sand out, you will have some areas that will need touch up and create knit lines anyway. For this reason, I would let cure enough now to allow sanding flat, go up to at least 600 grit to smooth layer transition (even 800 or 1000 if you have it), then add more poly. Good luck! Solvent poly is not fun to rub out anyway.

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Keith Kelly

223 posts in 1131 days


#4 posted 01-13-2015 04:00 AM



One of your problems may stem back to the BLO. Polymerization (hardening) of BLO is a very slow process. It takes weeks, months, even longer and may be contributing factors to the problems with layering. However, having said that, it just may be that you did not allow enough time in between coats for drying and insufficient block sanding in between coats. From the pictures I really can not see the problem well. I would let it sit and cure/dry before doing anything.

- pjones46

I forgot to mention, my application of the BLO was from Jeff Jewitt’s quick oil finish schedule published in FWW, which is very minimal BLO applied just to the surface (less than 1Tbsp per square foot, and dabbed on rather than dumped), followed immediatelyi with a coat of shellac. It actually worked really well, and each coat of Arm-R-Seal dried very nicely as other non-BLO Arm-R-Seal projects have in the past. Perhaps this sheds more light on the process I used to help make things more relevant.


Which coat(s) of your finish schedule did you apply too thick, #3? The arm-r-seal and poly are essentially the same. I think your conundrum is whether to keep adding poly before full cure so each coat can burn in, and not have what I call knit lines (layers that do not burn in or “knit”), and hopefully have a smooth film when finished, or let it cure more so you can sand flat now, add more poly later, but end up with knit lines.

Sorry but I can t answer for sure. I think it would have been best to sand out when it 1st happened. I suspect if you add more poly, let cure, then sand out, you will have some areas that will need touch up and create knit lines anyway. For this reason, I would let cure enough now to allow sanding flat, go up to at least 600 grit to smooth layer transition (even 800 or 1000 if you have it), then add more poly. Good luck! Solvent poly is not fun to rub out anyway.

- OSU55

I think I applied the first few coats of Arm-R-Seal too thick, so probably 1, 2, and 3. I had trouble getting the hang of it on as large of a surface of this (the big one is about 6’ x 4’). By the time I came back around to my second pass, the first coat had already started setting up, so most of the issues I have are noticeable overlap marks.

You nailed the conundrum.

Ok I think I’m going to wait it out and just chalk this up as a learning experience. 99.95% of the surface area turned out better than expected, and I definitely don’t want to ruin that.

About an hour ago, I did try something weird that seemed to help. But, it was too easy so maybe it’s just a mind trick. I rubbed 2 fingers across it really quick for about 30 seconds until my fingers heated up and started to burn. I feel like it somehow reduced the depth of the thicker layer. There’s still a line, but it looks more like a small line than one side being taller than the other. I did this in places near the edges and I’m fairly certain this helped. Maybe it just changed the sheen, or maybe it just changed the shape of my fingers or killed some nerves in my brain, but I feel that it helped, and that’s all that matters right? :) I wonder if there’s some point in the curing process where some heat might do good for leveling?

Regardless, I’m considering it done, will install it tomorrow, and will revisit it in a month to see what some light buffing does.

Thanks for the replies.

-- Keith - Bolivar, Missouri, http://www.SquareOneWoodworks.com

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pjones46

986 posts in 2111 days


#5 posted 01-13-2015 04:45 AM

Please keep us posted as it is an interesting situation. Thanks for sharing.

-- Respectfully, Paul

View Keith Kelly's profile

Keith Kelly

223 posts in 1131 days


#6 posted 01-13-2015 03:33 PM



...whether to keep adding poly before full cure so each coat can burn in, and not have what I call knit lines (layers that do not burn in or “knit”)...

- OSU55

Wait, so if Poly is applied before fully curing (say, immediately once no longer tacky), does the new coat burn in with the old coat?

If that’s the case, that would indicate that leveling later might not be a big deal.

-- Keith - Bolivar, Missouri, http://www.SquareOneWoodworks.com

View Fred Hargis's profile

Fred Hargis

3950 posts in 1961 days


#7 posted 01-13-2015 05:06 PM

Keith, I would wait until you can flatten the surface and see what you have. I don’t think you can actually repair the “witness” marks, but they may not be that noticeable. I do leveling (flattening) on those surfaces I want a glass smooth surface. After I get it smooth, I usually apply one last coat of wipe on varnish (I don’t use polyurethane formulas, but rather an alkyd resin formula). This is a slow way to get a smooth finish, mostly because of how long it takes for the varnish to cure enough to be flattened. As an aside, Arm R Seal is just a urethane varnish, much the same as whatever “polyurethane” you put on it although the Arm R Seal claims to be about 60% thinners on the MSDS (pretty thin).

-- Our village hasn't lost it's idiot, he was elected to congress.

View TheFridge's profile

TheFridge

5765 posts in 954 days


#8 posted 01-13-2015 06:24 PM

I’ve had drips and runs I’ve scraped out with a card scraper.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View Keith Kelly's profile

Keith Kelly

223 posts in 1131 days


#9 posted 01-13-2015 07:31 PM



I ve had drips and runs I ve scraped out with a card scraper.

- TheFridge

  1. Were they thin layers of poly?
  2. When did you scrape? After full curing?

-- Keith - Bolivar, Missouri, http://www.SquareOneWoodworks.com

View OSU55's profile

OSU55

1063 posts in 1457 days


#10 posted 01-13-2015 10:09 PM

You could scrape when the finish powders with sandpaper.

As for solvent poly burn in, some say there is a window, dependent on film thickness (thicker film, longer window), that solvent poly will burn in some and not have knit, witness, layering issues. I’m guessing a max of 24 hrs after the tackiness is gone. I haven’t tested it. I don’t use solvent poly for a filled finish. I attempted it once and decided a partially filled surface would have to do. I use WB products that dry more quickly and build film thickness quicker. If the knit lines are feathered well, like painting a car, they are difficult to notice.

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TheFridge

5765 posts in 954 days


#11 posted 01-14-2015 12:22 AM

After a day or 2 or 3. Drips and runs. I just skewed the scraper and used it as a cutter to get the big stuff, then leveled it out by scraping normally. I just made sure the edges didn’t did in.

Edit: it was probably as soon as I could do it it since I’m impatient.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

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