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I have only recently begun experimenting with linseed oil and walnut oil finishes, after mainly using mineral oil. Today I read this question and realized that my process may be flawed, because I am not pausing at all between applying linseed oil and then finishing with a carnauba wax topcoat.

I found this reference about drying oils in the above-mentioned question, but there's no real indication of how to tell by touch/sight when the curing process has completed.

Right now, my process is:
* Scrape or sand the bowl to a medium grit, usually 220
* Wipe gently with mineral spirits to remove dust in the grain and raise the remaining grain for finer grits of sandpaper
* Wait 1-5 minutes for excess mineral spirits to dissipate/evaporate (sometimes I try to hasten this using puffs from my mini air compressor)
* Sand up to my finishing grain, usually 600 grit and then 0000 steel wool
* Wipe with linseed oil until surface is covered; use a fresh rag to remove excess
* (note, no pause between previous step and this) Apply carnauba wax and buff into surface

...my question is, am I making a mistake here by not waiting for the linseed oil to cure before sealing it in with carnauba wax? If so, how long should I wait / how will I tell when it's OK to proceed to the final wax step?

Thanks for any help/advice you can provide!

AKA
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  • I think the bottom line for this is if it's working all right for you then go ahead and continue doing it. Numerous finishing steps aren't just possible over oils that haven't cured, it's actually the norm (despite what people say or believe they're doing) because of course nobody waits a month before they do the next stage. You just need to wait long enough for whatever comes next to work right, and presumably that's exactly where you are now. So no need to change, unless you notice a problem. – Graphus May 29 '19 at 16:45
  • What's the oldest piece finished this way that you still have that you can examine? Not asking because I think you'll find a problem (quite the opposite in fact, I fully expect that you won't). – Graphus May 29 '19 at 16:47
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    There's the rub - I've only recently started using linseed oil instead of mineral oil, and all the pieces I've finished with BLO have left my studio. And I never had the foresight to hold off on wax over the BLO to see how the finish matures.
    I guess I'll turn an experimental piece and mask off parts to see how different approaches pan out.     – AKA May 29 '19 at 22:22
  • Since posting my Answer I was reminded of friction polish, which as a non-turner I tend to forget about. Was wondering if you'd tried this? Well worth you looking into as you already have one of the chief ingredients, the BLO. – Graphus Jun 01 '19 at 05:09

2 Answers2

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am I making a mistake here by not waiting for the linseed oil to cure before sealing it in with carnauba wax?

I don't think so, no.

A seemingly logical worry here is that the carnauba will seal the surface and prevent the BLO underneath from curing, but that's not a valid concern because a wax finish doesn't seal a surface off at all. It's far too thin for that, so it's highly porous to oxygen, just as it is to liquid water and water vapour1.

how long should I wait / how will I tell when it's OK to proceed to the final wax step?

There's some personal interpretation/gut feeling in this for most people doing finishing. As mentioned in previous Answers and in my Comment above, in actual fact virtually nobody waits for their BLO application to cure before they proceed to the next step. Even if they say something like "I leave it overnight to dry" obviously 8-12 hours isn't nearly long enough for a coat of BLO to fully cure, but it 'dries' enough that they can proceed to the next step.

And that really is the key thing after you apply BLO2, has it cured enough for the next step to work right?

Back in 2014 or 2015 after reading about a quick one-day finish that started with oil and went on to shellac very quickly I started experimenting with applying shellac soon after oiling and I've done this regularly since, eventually reducing the wait to nothing. I've concurrently done other pieces where I left the oil overnight to 'dry', deliberately for comparison purposes. And there's no difference that I can determine in how the pieces finish or age subsequent to that3.

I fully expect wax on top of oiled wood to work just as succesfully, and for there to be no noticeable difference between waiting zero minutes, five minutes or overnight before waxing.

1 This is equally true for both lacquers and varnishes at this coat thickness BTW.

2 Including when you're doing a straight oil finish with nothing else added or put on top.

3 I subsequently learned from old finishing guides that oiling just prior to shellac being applied is nothing new and has been done for nearly as long as shellac has been used in wood finishing.

Graphus
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  • Thanks! The magic sentence I was hoping to hear was "in actual fact virtually nobody waits for their BLO application to cure before they proceed to the next step" ;-) – AKA May 31 '19 at 15:40
  • Welcome. One detail I didn't feel was necessary to include here that normally I would (because you're turning) is how carefully to remove the excess oil. With the wood spinning under the rag you'll naturally remove the excess oil far more easily than with a static piece, where you have to be pretty careful about it. – Graphus Jun 01 '19 at 05:04
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As far as I know linseed oil does not "cure" at all. As with most oil finishes, it serves to enhance the look, resist some staining, and protect the wood from drying out. However almost all oil finishes (including linseed) require upkeep to be effective. When treating wood with linseed oil you should be frequently re-oiling the wood as the existing oil will dry out over time.

I generally follow:
Apply first coat
Apply again 24 hours later
Apply again 7 days later
Apply again 1 month later
Apply again 3 months later
Apply again 6 months later
Apply every year for the remaining life of the wood (or sooner if the wood appears to be drying out).

If you are only looking to oil for aesthetics and not protection I see no harm applying the wax immediately after as Graphus has said, although I don't see much benefit in it.

Personally I only use finishing waxes on moving parts that need to slide with reduced friction. They provide little protection and you can get a better sheen from a shellac or varnish.

They also sell some oil/wax combos and oil/varnish combos that work just fine as well.

jesse_b
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  • Linseed oil is the premier 'drying oil' historically in the West, and like all drying oils is does cure (although curing is far faster and more reliable with processed oils than with raw). You can see curing in action for yourself by putting a drop of the oil on a glass or glazed ceramic surface, it should stay liquid for no more than a couple of days and then gel, and will eventually achieve a sort of leathery hardness. Totally agree with you on shellac or varnish versus wax in general, but the context of the Q is woodturning and turned objects are frequently finished in wax. – Graphus Jun 28 '19 at 08:00
  • BTW re. the need to oil yearly for life, my experience is that this isn't always necessary (as I suspected it wouldn't be). First thing I finished in BLO years ago was an oak stool and as far as I could tell it looked unchanged ~4 years later after having zero maintenance. It would have been very different if it had been a table and the top was being wiped regularly with a damp cloth and it's from that sort of use that I think the tradition comes from. – Graphus Jun 28 '19 at 08:04