When I put polymerized linseed oil on a walnut dish, lots of sanding scratch marks became visible. I wiped the surface oil off with mineral spirits before re-sanding. Next application of oil left the piece very dull. Can I put wipe-on poly over it? Do I need to wait a few weeks for the oil to cure? Thanks.
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Wipe-On Poly over Polymerized Linseed Oil
- Thread starter Ed Weingarden
- Start date
Why remove the surface oil? I would just keep sanding but leave the oil as is.
Yes you can put poly over the oil since you wiped off the excess. How long to wait depends on the poly application. If you are going to apply it like oil, ie keep wet for 20-30 min and wipe off, a couple of days is enough. If you plan to build a film, let the oil cure for a couple of weeks.
Some years ago I tested whether oil first then wo poly vs only wo po had any advantage for “popping the grain”. I used regular poly thinned 1:1, applied like oil or DO, keep wet 20-30 min then wipe off. My conclusion was a very very slight difference attributted the the slightly darker color of the oil. Adding a small bit of dye to the poly to give ~the same color as the oil resulted in equal results, with the poly actually looking better due to the very thin film on the surface that results (at least that’s what appears to happen) when the piece is flooded then wiped off. I use semi gloss poly so that negative grain or defect areas dont have hi gloss, but the top surface can be buffed to the gloss desired.
Oils dries soft. Leaving oil on the surface results in a soft wrinkled mess. Put a drop of oil and a drop of poly on a non- porous surface and let cure, or look at the cap and spout of the oil container bs poly on the outside of the container. Very different physical properties once cured.
Doug, in the original post they wiped the surface oil off with mineral spirits before resanding, not just wiping off the excess. I'm not sure I see a purpose in chemically removing the oil rather than just going ahead and sanding
Doug's first paragraph is what I was going to say.
Regarding the dull look after re-sanding- that does not surprise me, it is what can be expected with just one oil application. The wood was probably just as dull before that first oil coat, even if sanded to fine grits. The first coats of straight oil, raw or polymerized, will always soak right in, accentuating the grain colors, but not doing anything for the surface appearance. Depending on the wood, straight oil will start to remain more on the surface around a 3rd or 4th application, I've found, characterized by blotchy penetration. If I'm finishing with only oil, that is when I know for sure to not bother applying further coats. Further coats will remain on the surface more with each coat, and do little inside the wood. You can use this to your advantage with the extra coats, lightly wiping down each of them to avoid blotchy looking patches, but now the oil at the very surface will in itself cure into a top coat. Nowhere as tough as resin-containing oil (aka varnish), and without any obvious, unnatural reflective sheen, but the coats should look better as you add more, but it takes lots of time to cure all those coats.
For me- one coat of oil pops the grain, but looks flat/dull, as you observed. A second coat may help the first coat with the grain appearance a bit, but only improves the dull wood surface appearance a little bit. A third coat, it won't penetrate too much more, but after that coat is buffed with a soft cloth or paper towel, the overall appearance is looking pretty good, no longer dull, but no obvious plastic surface layer, either. This is where I normally stop, and I'm using polymerized oil myself (Tried and True products). Most times with dense woods, I'll stop after 2 coats. Rock hard, oily woods like cocobolo, you get to apply one very light coat of straight oil and it's not accepting any more after that, and you have to watch for bleeding oil for a few days, or longer, wiping it down well when found. (Watch what the wood is trying to tell you.)
I'm not looking for obvious surface films myself, but I could keep going with 4th, 5th, or more oil coats to start creating a surface film low sheen, but I need to be careful of those blotchy patches where the oil just is not soaking in anymore. I don't watch those blotches to cure on the surface, because they look awful.
I'd give plenty of time for the straight oil coats to cure before a final top coat of wipe on varnish (such as Watco, Waterlox, homemade wiping varnish concoctions, etc.). The test I use for checking cured oil finishes is this- wash and dry your hands well to remove skin oils. Look at the surface of the wood carefully under good light, make sure it is dry on the surface and not looking or feeling oily. Then pinch the wood firmly and hold that pinch for 30-60 seconds. Let go and immediately look at the surfaces where your fingertips were pinching, under good light. Move it around under the light. Do you see oily fingerprints, obvious or even the slightest hint of them? Then the oil has not fully cured. (Wipe off the oily fingerprints so they don't cure on the surface.) Do this in a patch of side grain wood and end grain wood, the end grain may show oily fingerprints for a longer duration, may need more days of curing. Be patient and try this every couple days until you get to the point of no oily fingerprints for several days running. Now your oil finish is likely fully cured, and if you've been watching a calendar, you'll see that maybe a week, or three or so, had gone by. Patience with oils, patience... The more coats of oil, they longer the curing process, maybe a full month.
Too much time? Try one coat of oil, applied and wiped/buffed on the lathe, and apply no more. Remove and set on a wire rack elevated off the table part of an inch so air gets all around it. Warm air, above 70. Do the finger pinch test, it'll probably show dry with a week. Then continue your finishing process as desired with the wipe on varnish products, building as much as you please.
I've posted in recent months about a couple version of warming/curing kilns to help speed the oil curing process. Just don't go crazy with the heat.
Regarding the dull look after re-sanding- that does not surprise me, it is what can be expected with just one oil application. The wood was probably just as dull before that first oil coat, even if sanded to fine grits. The first coats of straight oil, raw or polymerized, will always soak right in, accentuating the grain colors, but not doing anything for the surface appearance. Depending on the wood, straight oil will start to remain more on the surface around a 3rd or 4th application, I've found, characterized by blotchy penetration. If I'm finishing with only oil, that is when I know for sure to not bother applying further coats. Further coats will remain on the surface more with each coat, and do little inside the wood. You can use this to your advantage with the extra coats, lightly wiping down each of them to avoid blotchy looking patches, but now the oil at the very surface will in itself cure into a top coat. Nowhere as tough as resin-containing oil (aka varnish), and without any obvious, unnatural reflective sheen, but the coats should look better as you add more, but it takes lots of time to cure all those coats.
For me- one coat of oil pops the grain, but looks flat/dull, as you observed. A second coat may help the first coat with the grain appearance a bit, but only improves the dull wood surface appearance a little bit. A third coat, it won't penetrate too much more, but after that coat is buffed with a soft cloth or paper towel, the overall appearance is looking pretty good, no longer dull, but no obvious plastic surface layer, either. This is where I normally stop, and I'm using polymerized oil myself (Tried and True products). Most times with dense woods, I'll stop after 2 coats. Rock hard, oily woods like cocobolo, you get to apply one very light coat of straight oil and it's not accepting any more after that, and you have to watch for bleeding oil for a few days, or longer, wiping it down well when found. (Watch what the wood is trying to tell you.)
I'm not looking for obvious surface films myself, but I could keep going with 4th, 5th, or more oil coats to start creating a surface film low sheen, but I need to be careful of those blotchy patches where the oil just is not soaking in anymore. I don't watch those blotches to cure on the surface, because they look awful.
I'd give plenty of time for the straight oil coats to cure before a final top coat of wipe on varnish (such as Watco, Waterlox, homemade wiping varnish concoctions, etc.). The test I use for checking cured oil finishes is this- wash and dry your hands well to remove skin oils. Look at the surface of the wood carefully under good light, make sure it is dry on the surface and not looking or feeling oily. Then pinch the wood firmly and hold that pinch for 30-60 seconds. Let go and immediately look at the surfaces where your fingertips were pinching, under good light. Move it around under the light. Do you see oily fingerprints, obvious or even the slightest hint of them? Then the oil has not fully cured. (Wipe off the oily fingerprints so they don't cure on the surface.) Do this in a patch of side grain wood and end grain wood, the end grain may show oily fingerprints for a longer duration, may need more days of curing. Be patient and try this every couple days until you get to the point of no oily fingerprints for several days running. Now your oil finish is likely fully cured, and if you've been watching a calendar, you'll see that maybe a week, or three or so, had gone by. Patience with oils, patience... The more coats of oil, they longer the curing process, maybe a full month.
Too much time? Try one coat of oil, applied and wiped/buffed on the lathe, and apply no more. Remove and set on a wire rack elevated off the table part of an inch so air gets all around it. Warm air, above 70. Do the finger pinch test, it'll probably show dry with a week. Then continue your finishing process as desired with the wipe on varnish products, building as much as you please.
I've posted in recent months about a couple version of warming/curing kilns to help speed the oil curing process. Just don't go crazy with the heat.
@Doug Freeman & Steve Tiedman - thanks for the detailed information. I have no problem waiting weeks, if need be; I always have other projects to work on.
Winner-winner, Ed. All the best...
Another option, besides removing the surface oil with mineral spirits, is to just wipe off the excess before it starts to dry/cure, and then wet-sand with the same oil. Wet sanding can help get the oil deeper into the wood as well, and lubricate the sanding process. Over time, with multiple coats, you can build up the sheen you desire.
@Jon Rista - good suggestion. I'll keep that in mind the next time I have to re-sand 
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