Okay, I have a a folow-up question to my earlier one concerning sanding thru finish coats. To summarize, I am going to be applying multiple coats of Watco Danish Oil and after the 2nd coat start wet sanding with 400 grit.
My question is: when wet sanding, how do I tell that it is time to stop and let it dry? All instruction I have ever seen simply says wet sand with XXX-grit paper but never for how long.
Thanks.
Replies
Pat,
Until you're confident that you've evenly gone over the whole surface.
After the second coat, the wood will be completely sealed and it's no longer necessary to leave the finsh on so long before wiping "dry." About 10 minutes will do.
You can wipe to check your progress as you "sand." It's more like oiling the wood than sanding. Just evenly rub with the 400 grit pad or with the paper held in your hand as thoroughly as you can with the grain. On my final wipe "dry" I try to leave just a barely glistening surface by wiping with a "french polishing" motion using a rag balled up into a tight pad.
Rich
pat,
I've done this working up from 400-600 grit to 1000-2000. You really can't hurt it if your relatively gentle...and use your hands to feel if it's smooth. You judge by feel and looking at the wood..
Remember that oil/varnish mixtures like Watco can not be built up effecively. When you apply the first coat, the oil and some of the varnish penetrate the wood while the rest of the varnish ends up on the wood. This "extra" is what is wiped off when you wipe the surface. The varnish in the wood dries sealing up the wood and preventing further penetration. If you then sand in another coat, you are catching areas that have not been fully penetrated with the oil and smoothing the surface. When you wipe off this coat and let it dry, no more of the Watco will be absorbed. Further applications are not absorbed at all. Instead, a very thin film of oil heavy varnish is left on the surface and you end up with a soft finish. Continuing to attempt to build can then lead to a gummy surface.
Watco, and other oil/varnishes, are intended to be an in the wood finish, not a film finish. Their beauty is that you can see and feel the grain of the wood to a greater extent than you can with a film finish.
Howie,
Oil/varnish mixtures such as Watco actually do build a film of varnish as many coats are applied. There is no reason to predict a gummy surface with many applications any more than with 2 or 3.
The varnish layer cures as hard on the 4th and subsequent coats as it does on the 2nd or 3rd. The oil simply acts as a lubricant for the abrasive once the wood has been sealed. On many woods, there is a visible improvement with 4 or 5 coats and the protection is better with the (very slightly) thicker varnish film. The driers in the varnish accelerate the curing of any residual oil left on the surface. I've never had one of these finishes get gummy. The only real problem with them is that, while pretty, they are too delicate to withstand any significant use (like frequent abrasion from hands and forearms on the arms of a rocking chair).
I've also had them wipe right off down to bare wood with certain oily woods (teak especially) when attempting to clean them with mineral spirits as long as 2 years after applying.
Applying multiple layers of these finishes is one of those efforts that finally stop when you've gotten tired.
Rich
Okay, thanks Rich and everyone else for your insights. Here is another question in the same vein: What kind of cloth do you use to wipe on finishes like this? Is T-shirt material acceptable, cloth diapers? I always hear about using a lint free cloth and have never been able to tell what cloths were lint free. Thanks again.
Pat,
Any thin cotton material that's been washed is lint-free. T-shirt material is just fine. HD, Lowes sells the stuff in boxes (washed and ready to use). If you shake out a few handfuls and fabric lint falls out, throw the whole batch in the washer and dryer and you'll be good to go.
Be careful though, I got a batch once that was velour cloth. You don't want that. It was terrible. It shed like crazy. Ugh! I guess their supplier of cloth remnants screwed up on the "quality control."
Rich
Pat,
I use my hands...warms the liquid slightly and spreads a nice thin coat. A splash of mineral spirits and a wipe with a paper towel cleans my hands. Underware is good to use..but all mine is only 30 years old so.....
Thanks, Rich an BG. I still need most of my underwear, so I gues I'll be going to HD!
:-))
Rich,I'm curious about your experience with oil finishes on rocking chairs. I"m planning on building a pair of rockers (my first) and based on my web research, I was planning on an sanded oil finish, topped with carnuba wax. I've had good results with this finish on other items, but obviously a rocker gets more abuse.The chairs are to be white oak and cherry.Tom
tms,
Sam Maloof makes some of the most gorgeous rocking chairs on the plant. He also gets gorgeous prices for them. His finish is a 2 part oil/varnish, then a wax mixture (can't remeber the ingredients right now - they're no secret - can be home brewed or bought from him).
I can post his method later.
I don't think you will have any problem with the woods you're using and an oil/varnish/wax finish.
Rich
>>The varnish layer cures as hard on the 4th and subsequent coats as it does on the 2nd or 3rd. The oil simply acts as a lubricant for the abrasive once the wood has been sealed.What do you mean by "varnish layer"? Watco is a mixture of oil and varnish--the two are fully mixed and are not able to be separated. After the first two applications are dry, putting on more and then wiping it dry will remove almost all of the oil and varnish whether it was sanded in or just wiped on. Whatever little amount that is left on the surface is still oil and varnish. There is no varnish layer.But, if you like the finish produced by multiple applications of an oil/varnish finish, then, by all means, continue.Howie.........
Howie,
With each additional application, a small amount of the varnish and the oil in the oil/varnish mix is left on the surface to cure. Wiping "dry" is just a figure of speech in this regard. The more that is wiped from the surface, the less to cure. I, and many others wipe to a glistening film, not "dry" (less glistening but still there).
Granted, it's not much, but to claim that there is no varnish and oil film left behind or that a cured film does not form is wrong. The film builds very slowly and is thin and delicate. The technique is the same as any "rubbed varnish" application.
Have you ever poured a puddle of linseed oil or tung onto wood and let it cure? That's a heavy application compared to the typical "danish oil" technique. But it demonstrates very clearly that oil forms a film finish. I really don't have to prove that varnish, even in small amounts forms a film finish, do I?
Rich
>>Have you ever poured a puddle of linseed oil or tung onto wood and let it cure? That's a heavy application compared to the typical "danish oil" technique. But it demonstrates very clearly that oil forms a film finish.Yes I have Rich, but I have done it on glass or on metal. I've done maybe 20 times in classes I have taught. Doing it on wood where it is absorbed will not give a true picture of the "hardness" of the resulting film. To see what happens I recommend you get out a copy of Flexner's "Understanding Wood Finishing". There are a number of photos in the section explaining the difference between a thinned wiping varnish and an oil/varnish mixture. The thinned wiping varnish does dry flat and smooth. The oil/varnish dries with a crinkly soft glob.Howie.........
"The oil/varnish dries with a crinkly soft glob"
Yes, a very thick film of it does. And if given enough time the crinkly glob becomes a VERY hard crinkly barnacle, strongly adherent to the wood and tough as nails
The point being argued was whether an oil varnish mix forms a surface layer. At least you now agree it does (although you continue to disparage the quality of that layer).
But multiple layers, put down very thin and abraded with very fine, lubricated abrasive (4-0 steel wool, 400-600 grit wet or dry silicon carbide paper), dry/cure rapidly to the hard state without any crinkles whatsoever.
Anyway, it's silly to go on with this. Anyone who has built up a finish with this stuff knows how it "builds." And anyone who hasn't tried it can very easily find out.
Me? I prefer to mimic an oil-varnish look with spray lacquer anyhow. To each his own
Rich
Rich is absolutely correct. I don't know what information or experience you may have had with a "gummy" appearance from multiple applications of oil/varnish, but that just doesn't happen. Oil/varnish mixtures do build a film that is silky smooth. Touch a Maloof rocker and tell me there is not a film there and I gurantee it came from multiple applications.
If you continue to wet sand after even the first coat, follow BG's advice and work up in finer grits. My own technique is to only sand the first initial saturation coat, sand till it's almost dry then apply more oil and let it sit a bit before wiping off. Subsequent coats (at least two) are applied via an oil soaked rag. Since the wood won't really soak up any more, there's no point in wasting any. You can vary this by applying with some 0000 steel wool. Buff with clean rags. I've had good results applying oil on hot sunny days....do it in the sun. The heat seems to dry the oil faster and you can get a nice rubbed out "build."
The more coats you apply, the better the wood/finish will look. In my own case, I've always run out of "elbow grease" before I'd applied too many coats to get gummy.
By the way, I've found that used linen napkins make killer rags. You may find a source for these at a commercial laundry near you.
Thanks JPatrick. I'll keep your advice in mind as I proceed. Appreciate the help!
VIVA! (by Kleenex) -- cloth-like, not embossed, wonderful.
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Another proud member of the "I Rocked With ToolDoc Club" .... :>)
"Have you tried wood "flour" on the unwanted glue?" Not yet, the only glue I've used in the past few days has been epoxy on jig pieces I'm not finishing. Don't have any glue-ups in my immediate future, maybe I'll do one just for fun!
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Another proud member of the "I Rocked With ToolDoc Club" .... :>)
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