What's going on with this finish

[Sam Murdoch]

Well........the battle orders I operate under say no sanding required between coats if I can get the 2d coat down in 12 - 24 hours. Beyond 24 hours I sand. Usually I'll wait 36 - 48. If you are getting gummy stuff, then it isn't dry enough, I'd guess. I get fine, amber dust.

Kent, I follow the same orders with these products, though I don't usually wait much longer than the 24 hours. A good brushed on coat with proper drying and humidity is 98% of the time ready for sanding from one day to the next + a few hours. I can tell very fast if the finish needs more dry time. I never wet sand unless I am at 5 or 6 coats and going for a mirror finish.

[Alan Lightstone]

You can dry or wetsand between coats. It's not really needed for adhesion purposes - just leveling. If yr surface is smooth 'enough' you'll be able to buff out minor imperfections and dust in the end. I choose to wetsand with MS between every couple coats because I find it a little less aggressive than dry sanding, and I tend to get corns when dry sanding.

Newer stearated sandpapers (according to Jeff Jewitt) are a better choice because they let you see what yr doing better, can used dry, and don't leave material that is incompatible with most varnishes. I used this kind of 'carborundum' sandpaper once and it was wonderful.

I just use it for leveling also, not adhesion.

Which of the newer stearated sandpapers do you use?

[Jon Middleton]

Interesting thread. Why are you sanding between coats with 600 grit? I have used worn 220 and it works fine. All you're trying to do is knock out dust nibs or other high spots. I applied a second coat of Behlens Rockhard today, thinned ~5% to aid leveling. This went over the sealer coat which was thinned 50/50 with MS. I used P320 for it, as I didn't want to cut through. I'll be filling the pores with the finish itself, which means removing lots of finish because of the porosity. Seems to me that the P320 or even 220 is fine.

[Phil Thien]

This has been a very informative thread.

I learned at least three things I did not know about finishing.

[Prashun Patel]

It was a red stearated paper that is private labeled for the company that makes Bush Oil. I believe it is the same as Carborudum Premier Red dry lube auto paper but that has not been confirmed.

[Alan Lightstone]

Interesting thread. Why are you sanding between coats with 600 grit? I have used worn 220 and it works fine. All you're trying to do is knock out dust nibs or other high spots. I applied a second coat of Behlens Rockhard today, thinned ~5% to aid leveling. This went over the sealer coat which was thinned 50/50 with MS. I used P320 for it, as I didn't want to cut through. I'll be filling the pores with the finish itself, which means removing lots of finish because of the porosity. Seems to me that the P320 or even 220 is fine.

I only use 600 grit between the next to the last coat and the wiped on coat typically. That way I get a very smooth finish. I used it earlier on this piece as I had roughed it up substantially with the 320, then even the 400 as I wanted a smoother finish. This piece is a present for my wife, and I really want it to be show quality, or at least the best I am capable of.

That being said, after brushing on the coat, the surface is pretty rough again, so I'll have to repeat the sanding before the last coat.

I'm sure there are better approaches, and I'd love hearing from the true finishing gurus, but this is my routine.

[Alan Lightstone]

This has been a very informative thread.
I learned at least three things I did not know about finishing.

I'm guessing those three things are:

1. That I have a lot to learn about finishing.
2 and 3. See #1 above.

[Kent A Bathurst]

Kent, I follow the same orders with these products, though I don't usually wait much longer than the 24 hours. A good brushed on coat with proper drying and humidity is 98% of the time ready for sanding from one day to the next + a few hours.

I agree with the 24 + a few, in general. Temp + humidity in my unheated 85-yr old basement, with direct access door to the outside, is "comfortable" even in winter, but I don't generally varnish until mid-afternoon to let the temps get >65 before varnishing. AM temps usually around 60 this time of year.

So - the way the clock works out is that the 24 hours + a few puts me in range of the dinner bell - and is definitely after the sun is over the Bass Ale yardarm - so I let it ride till the next morning. Its a logistics issue as much as anything.

I just use it for leveling also, not adhesion.
Which of the newer stearated sandpapers do you use?

AFAIK, after 24 hours the sanding is needed to help promote adhesion.

I've never tried that paper, so no opinion. The stuff I really like is Norton 3X gold-colored 320. I like the backer paper, and the grit works well for me. An alternative would be the 3M 261U, but I like the Norton better in 320. I also have some Norton 400, but that didn't seem to add any benefit v 320, and the 320 cuts a bit faster.

I use the 3M in P600 for other situations.....especially smoothing between coats of shellac. It's really good stuff, IMO.

[Alan Lightstone]

AFAIK, after 24 hours the sanding is needed to help promote adhesion.

I've never tried that paper, so no opinion. The stuff I really like is Norton 3X gold-colored 320. I like the backer paper, and the grit works well for me. An alternative would be the 3M 261U, but I like the Norton better in 320. I also have some Norton 400, but that didn't seem to add any benefit v 320, and the 320 cuts a bit faster.

I use the 3M in P600 for other situations.....especially smoothing between coats of shellac. It's really good stuff, IMO.

This is from Waterlox's website:


Sanding and Waterlox.

Sanding for adhesion purposes is not required between coats of Waterlox Original Tung oil finishes. This makes Waterlox unique and different from most surface finishes which need abrasion for inter-coat adhesion.

Most surface finishes such as urethanes require the sanding process to create what’s called a “profile”. A profile is similar to a mountain range microscopically. Failure to sand/abrade between coats of a surface finish can result in delamination of the new coat from the old coat. With Waterlox Original Tung oil finishes, new coats will actually bond with the previous Waterlox coat and becomes part of it rather than a layer on top of it.

Even on a finely sanded wood surface, there are peaks and valleys as well as spots of hard and soft grain. When you apply the first coat of Waterlox, it’s like snowfall on the mountains. The snow caps the peaks and begins to fill the valleys. If you sand, you will unseal the caps and there will be less to flow to the valleys when you apply the next coat of finish. This will result in the cap being re-sealed again, and will therefore result in less available finish to flow into the valley. If you do not sand, then the next coat will flow away from the sealed caps and do more to fill the valleys. After the third or fourth coat, this self-leveling process is complete.<sup>1

1</sup>This is the most important reason to obtain the recommended spread rate of 500 square feet per gallon per coat.

ABRASION TECHNIQUES FOR AESTHETIC REASONS FOR FLOORS:

• Heavy debris or applicator fuzz can be removed from the film with 0000 steel wool, 320 grit sandpaper, or a Scotch-Brite® pad (as shown in the Waterlox application video on our website at waterlox.com.)
• Some customers perform a light buffing between the second-to-last and last coat. This is for aesthetic reasons only. Depending on the size of the project you may choose to use a new or used maroon pad or a 3M® white pad with a low-rpm buffing machine. For smaller rooms, try a drywall pole sander or an orbital sander with 320 or finer grit paper.
• Keep in mind if you can visually see any sand or swirl marks in the finish before the final coat, these need to be sanded or removed with a finer grit paper or pad before proceeding with the final coat as they WILL be visible. To check for sand or swirl marks, wipe a thin coat of mineral spirits over an area. While still wet it will give you an accurate visualization of what the final coat will look like.
• Waterlox Original Tung oil finishes should never be abraded with a coarser grit than 150.
• NEVER sand a surface that has been stained as this process will change the color.

TIP

Before using a new applicator, be sure that any loose hairs or fibers are removed or cleaned from the applicator. This can be achieved by any of the following methods:

• Wrap the applicator with masking or painter's tape and then remove the tape completely, or
• Put new and unused applicator pads in the dryer for a spin, or
• Use a lint roller on the applicator pad until the lint-roller paper does not pick up any further hair or remains sticky.

ABRASION TECHNIQUES FOR AESTHETIC REAONS FOR WOOD PROJECTS (e.g.: tables, furniture, etc.):
Follow the instructions "For Floors" as outlined above; however, because these type of projects are smaller in size you may want to perform a light sanding with 220 or higher grit sandpaper or 0000 steel wool. For fine woodworking, many artisans have used 600 - 800 grit sandpaper before the final coat.


So they are saying it's for applicator fuzz / dust nibs, not for adhesion. FWIW. Of course, they are also saying it isn't needed for leveling, and I find that is not always the case.

I'm pretty sure I don't quality as an artisan, but I do use the 600 grit before the next-to-last coat.

After reading this, plus Kent's advice above, I think I'll switch to Norton 3X gold-colored 320 for the leveling (especially since I'm finally all out of the 23yo sandpaper I used earlier), and stay with the Norton or 3M P600 for the next-to-last coat final sanding.

Has anyone used those Norton sanding pads that Woodcraft sells (they come in 500-600 grit, I think 800-1000 grit, plus probably coarser grits too.) Do they have any advantages over plain sandpaper?

[Prashun Patel]

Kent, (I'm getting out of my league here), but I have read that sanding POLYURETHANE is necessary after 24 hours for adhesion purposes. If you wipe on poly, you put down thin coats that can be recoated within hours of each other. In this case, the layers apparently link together, which is why you don't require sanding. However, after a day, the layer has dried enough that subsequent coats are laid on top, and distinct layers. Sanding promotes the mechanical bond here.

With Waterlox, I have always assumed the same phenomenon exists: quick, successive coats fuse; coats > 24hrs are distinct layers. The only diff is that Waterlox does not seem to require sanding to promote the mechanical bond as does poly.

I've often had to wait > 24hrs between WLox coats (usually wiped, no sanding btwn coats) and have not had any adhesion probs.

[Phil Thien]

I'm guessing those three things are:

1. That I have a lot to learn about finishing.
2 and 3. See #1 above.

LOL, pretty close!

I think the biggest thing is waiting enough time between coats.

I've used various wiping varnishes (well, mostly Formby's) and have always "pushed the envelope" when applying another coat.

I had once considered using Waterlox, and won't let this thread scrare me off. But if I do use it, I'll know not to use MS for wipe-downs, and to make sure I give each coat plenty of time.

[Chad Bender]

That being said, after brushing on the coat, the surface is pretty rough again, so I'll have to repeat the sanding before the last coat.

I'm sure there are better approaches, and I'd love hearing from the true finishing gurus, but this is my routine.

I'm no guru either, but I have been able to achieve some very smooth final finishes. I never assume that the final coat will provide the smoothness I'm after. Some nibs and dust are inevitable. I typically let that coat cure for ~1 month, and then rub it out with 0000 steel wool and a little soapy water. You could use other abrasives if you want a more glossy finish.

[Kent A Bathurst]

Prashun.........I don't use poly, but I'm sure you are correct.

As far as my approach on sanding......just following orders from a couple guys here that are smarter than me. Since it has always worked fine, that's what I do. My assumption is the same as your assumption.

I don't think this matters, but I use Behlen's except when satin is needed, and then it is Wlox for last thinned wipe-on coat or two.

[Alan Lightstone]

Prashun.........I don't use poly, but I'm sure you are correct.

As far as my approach on sanding......just following orders from a couple guys here that are smarter than me. Since it has always worked fine, that's what I do. My assumption is the same as your assumption.

I don't think this matters, but I use Behlen's except when satin is needed, and then it is Wlox for last thinned wipe-on coat or two.

Is the drying time / recoat time shorter for Behlen's?
Does it give the same warm amber tone as Waterlox?

Always looking for a better / easier / quicker way to do things, if possible.

[Kent A Bathurst]

Is the drying time / recoat time shorter for Behlen's?

Nope.

Does it give the same warm amber tone as Waterlox?

The "same" - I dunno. I think there is a bit of a difference in the color...one is a bit darker/deeper amber than the other..forget which is which. Both are a warm amber tone.


Always looking for a better / easier / quicker way to do things, if possible.

Rotsa ruck.

Also - Wlox is made from Tung Oil, Behlens isn't [BLO maybe?]. My understand is that means Wlox is a bit better at waterproofing. That doesn't matter to me, because I am using shellac seal coats after dye and after gel stain, so the shellac has that topic covered.