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View SMP's profile

Diminishing returns on coats of Danish Oil?

by SMP
posted 11-29-2018 10:15 PM


13 replies so far

View bondogaposis's profile

bondogaposis

5569 posts in 2910 days


#1 posted 11-29-2018 11:33 PM

Danish oil and BLO have lot in common and that they both have a a high BLO content. Once the wood is sealed, there no point putting more of either one of these on, as is will just make a gummy mess. You cannot make a film finish with oil.

-- Bondo Gaposis

View Manitario's profile

Manitario

2787 posts in 3441 days


#2 posted 11-29-2018 11:41 PM

Think of Danish oil as BLO with a bit of polyurethane added. I like using DO on my projects because the poly gives a bit of a sheen, but don’t think that the small amount of poly will provide much protection. If I want a project eg. a coffee table to have more protection, I’ll do a couple coats of DO and then several coats of wipe on poly. I suppose you could achieve the same with a ton of coats of DO but seems like a waste of time and finish.

I used straight BLO on my workbench; your workbench is going to get beat up with use (no finish is really going to prevent that) and eventually need re-finishing; BLO is the easiest to just re-wipe a coat on from time to time.

-- Sometimes the creative process requires foul language. -- Charles Neil

View CaptainKlutz's profile

CaptainKlutz

2024 posts in 2053 days


#3 posted 11-29-2018 11:52 PM

You are only adding hardness to surface. None of the finishes (even with added solvent) will be absorbed deep enough to add any significant strength to interior wood. Can check for yourself: Apply finish, and saw a piece of wood off. There will typically be less 3/32 inch of penetration, unless the wood is cracked/damaged.

Most Danish Oil’s are blends of oil (often BLO) and old school varnish resins. The oil hardens (thanks to metallic driers) and resin cures when exposed to oxygen. Once you get a couple of coatings applied and surface pores are sealed, the oil stops being absorbed and takes forever to dry/cure. Adding more finish once absorption stops is adding little value to final finish (IE Yes – Diminished return).
If you want a harder/thicker finish on work bench, need to use a Polyurethane, or spar varnish. Problem with film finish is they are tougher to repair when damaged. These are not something I would recommend for work bench.

My personal preference for hand tool bench finish is something I read online (forget where):
50:50 blend of Tried and True Original Wood Finish and Varnish Oil.

The resin in Varnish Oil seals the wood better than BLO alone, and the Beeswax in Original Wood Finish gives the top the right balance of not too slick or too sticky surface. The beeswax also prevents wood glue from sticking and drips can be scratched off with finger nail or putty knife easily. I coat the bench top with only Original Wood Finish as needed to maintain the surface (once every 12-18 months). Reapply the the 50:50 blend when I resurface/flatten the top with hand planes. My current bench is 5 yrs old now, and looks almost brand new every time I refinish it.

A friend/mentor of mine always used an old school homemade blend of BLO, Beeswax, Paraffin, Varnish and mineral solvents on his benches. Variations of it have been around for decades, maybe centuries; and formulas can be found online for DIY. For me, the T&T products are much simpler to buy and use. If T&T wasn’t available to me, I would be using home made BLO/wax blend for my bench(es). While straight BLO works well and is easy to repair, the wax prevents things like glue, or even drops of dye/stain/finish from being absorbed into bench top.

Best Luck.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View jutsFL's profile

jutsFL

191 posts in 400 days


#4 posted 11-30-2018 01:56 AM

I make my own varnish… Which is basically the same as a danish oil. Its one third mineral spirits, one third BLO, and one third semi gloss poly.

Ive noticed that about 4 coats is about my point of diminish. Any more than that and your talking extra weeks for a full cure.

As an example, I tested a few on some of my table apron scrap from an ongoing project. This has 4 coats of the mix and has dried for about 3 weeks . its done and cured now, but I belive I am going to do on last very light dilution poly and MS wipe on for the top.

-- I've quickly learned that being a woodworker isn't about making flawless work, rather it's fixing all the mistakes you made so that it appears flawless to others! Jay - FL

View SMP's profile

SMP

1443 posts in 464 days


#5 posted 11-30-2018 03:28 PM


You are only adding hardness to surface. None of the finishes (even with added solvent) will be absorbed deep enough to add any significant strength to interior wood. Can check for yourself: Apply finish, and saw a piece of wood off. There will typically be less 3/32 inch of penetration, unless the wood is cracked/damaged.

Most Danish Oil s are blends of oil (often BLO) and old school varnish resins. The oil hardens (thanks to metallic driers) and resin cures when exposed to oxygen. Once you get a couple of coatings applied and surface pores are sealed, the oil stops being absorbed and takes forever to dry/cure. Adding more finish once absorption stops is adding little value to final finish (IE Yes – Diminished return).
If you want a harder/thicker finish on work bench, need to use a Polyurethane, or spar varnish. Problem with film finish is they are tougher to repair when damaged. These are not something I would recommend for work bench.

My personal preference for hand tool bench finish is something I read online (forget where):
50:50 blend of Tried and True Original Wood Finish and Varnish Oil.

The resin in Varnish Oil seals the wood better than BLO alone, and the Beeswax in Original Wood Finish gives the top the right balance of not too slick or too sticky surface. The beeswax also prevents wood glue from sticking and drips can be scratched off with finger nail or putty knife easily. I coat the bench top with only Original Wood Finish as needed to maintain the surface (once every 12-18 months). Reapply the the 50:50 blend when I resurface/flatten the top with hand planes. My current bench is 5 yrs old now, and looks almost brand new every time I refinish it.

A friend/mentor of mine always used an old school homemade blend of BLO, Beeswax, Paraffin, Varnish and mineral solvents on his benches. Variations of it have been around for decades, maybe centuries; and formulas can be found online for DIY. For me, the T&T products are much simpler to buy and use. If T&T wasn t available to me, I would be using home made BLO/wax blend for my bench(es). While straight BLO works well and is easy to repair, the wax prevents things like glue, or even drops of dye/stain/finish from being absorbed into bench top.

Best Luck.

- CaptainKlutz

Interesting, thanks for all that. I had seen this old time finish recipe that I was going to use for a small box, but I thought the wax would make the bench slippery.
https://woodandshop.com/make-a-historic-beeswax-oil-turpentine-furniture-polish-finish/

Does shellac build up more internally to the wood since it soaks in deeper?
I’ll take a look at some of those other recipes, as I also need something for a kitchen countertop soon.

View JayT's profile

JayT

6325 posts in 2769 days


#6 posted 11-30-2018 03:35 PM

Too many coats of Danish oil will give a harder surface, but at the cost of making it slicker because of the varnish element. I use one or two coats and call it good. Don’t know any reason to wax a workbench—an assembly bench or finish station, yes, workbench, no. Any workbench will get dings and dents, a softer one will just get them faster. That’s OK, better to ding the bench than a project.

On the subject of commercial Danish oil building, the biggest issue most people run into is that they don’t let previous layers polymerize completely before adding a new layer, thus preventing the finish from being allowed to build.

-- https://www.jtplaneworks.com - In theory, there is no difference between theory and practice. In practice, there is.

View Kelly's profile

Kelly

2523 posts in 3503 days


#7 posted 11-30-2018 04:09 PM

I note many, including a purported, nationally known expert say finishes don’t penetrate. The so “expert” claimed the idea of penetrating finishes was nothing more than a promotional gimmick by Flecto-Varithane. That was at least twenty years back, and I argued with the expert for a few reasons.

When I mix poly about 50% thinner and slop it on dry wood, it disappears. In fact, I put about two gallons of thinned poly in a six inch slab and it soaked all the way through. When I dropped my applicator, bent to pick it up and looked up, the bottom was wet. Of course, until the finish was allowed to harden (subjected to air, it kept wicking and the wet spots grew.

[SIDE NOTE: Decades later, though having sat in front of a well used fire place insert, no moisture appeared to be gained or lost in the rather large piece of wood, thus no cracks or splits developed (as the piece dried out more).]

I don’t know if poly molecules are larger than turpentine or paint thinner, but I doubt it develops the property of evaporating merely because I apply it to wood and it remains it disappears when applied to the wood.

Then there is the fact that, when thinned poly is first applied, it can disappear almost immediately, but, as more is applied, it disappears slower and slower. Add to this, if you keep the surface wet, you can keep adding, but if you let the surface dry between application, applications of finish will pool.

Today, we know that we can “stabilize” wood by playing with it in a pressure/vacuum tank. Of course, this is just forcing finish deep into the wood. That the finish did penetrate is obvious by that the stabilized piece will become heavier.

As to hardening wood, it is full of little hollows by which the tree transferred nutriments. I think of these as Coke cans. If the can is full and a lid is on, we could stand on it and it wouldn’t collapse. Pop the lid and, even with the liquid inside, the can will crush [as the liquid moves outside the can].

_

As to Danish and similar “oils,” like Frombys, so called Tung Oil Finish or Teak Oil (do they really squeeze and steam teak trees for this stuff?), it is my understanding they are nothing more than BLO -based- finishes similar to what we call wiping finishes. In other words, they are just poly finishes thinned with BS marketing thrown in.

As to building coats with BLO or tung oil, I’ve built coats with both without the gummyness mentioned. However, after allowing each coat to sit for a few minutes, I wiped off the excess, then let the coat harden at least twenty-four hours, before adding the next. When done it looked just like a quality satin finish. Of course, subjecting the finish to abuse or moisture would tell a different tale.

View Fred Hargis's profile

Fred Hargis

5832 posts in 3052 days


#8 posted 11-30-2018 04:49 PM

The turp/beeswax/BLO mix is what I’ve used on my workbench, assembly table, and other wooden surfaces in the shop for quite some time. I first read about it over at the Wood magazine forum some years ago, tried and really like it. It’s easy to renew, glue pops right off, and pleasant looking enough. If I have a complaint about it, it’s 1) the smell of the turp lasts for several days, even with the windows open. I did find that dissolving the wax into the turp isn’t a 5 minute job, it takes a few days, and warm temps help. I set my jar in the mailbox (after the mail had been delivered) on a summer day to speed things up. I suspect it might work as well using MS in place of the turp, but haven’t tried it; I’d bet it would reduce the lingering odor.

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

View CaptainKlutz's profile

CaptainKlutz

2024 posts in 2053 days


#9 posted 11-30-2018 09:56 PM

FWIW:

Please do not confuse polyurethane with varnish, they are not same. From a chemistry stand point, then are often radically different.
While a varnish finish formulation can use a polyurethane resin, but it can also use alkyd, acrylic, and natural occurring resins like shellac or tree sap (rosin).
Example – Watco Danish oil uses proprietary rosin blend (tree sap) as ‘varnish’ component.

Won’t drive this thread further off topic with long explanation on why it is important to use proper terminology when describing wood finishing chemistry, but suggest a good read of wiki pages on common wood finishes for some background information.

https://en.wikipedia.org/wiki/Varnish
https://en.wikipedia.org/wiki/Polyurethane
https://en.wikipedia.org/wiki/Linseed_oil

Sorry to digress down this rabbit hole, I have spent half my work life involved with polyurethane and other polymer systems for electronics industry. Some of the generic names used above could be misconstrued by the uneducated. It is best to be very specific with chemistry when discussing DIY or modified wood finishes in a public forum.

Thanks for reading. Cheers!

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View OSU55's profile

OSU55

2450 posts in 2548 days


#10 posted 11-30-2018 10:54 PM

IMO a much better resource for understanding different types of finishes is the book “Understanding Wood Finishing” by Bob Flexner. As I read through the wiki links above I found them to be somewhat misinforming, especially the one for varnish. While CaptainKlutz is correct that polyurethane and non-poly varnish can be very different in the universe of coatings for all things, they are pretty similar for the products sold for wood finishing that the hobbyist and small shop owner are likely to use (not necessarily true for large production furniture mfg). There are only 2 non-poly varnishes marketed and sold today that I’m aware of, Pratt and Lambert #38 and Sherwin Williams Fast Dry Varnish. One thing we don’t know about poly varnishes is the amount of poly added in – none of the mfrs release specific information. Sometimes there is info on the oil and other resins used. Again just my opinion.

As for a bench finish, I just use poly thinned 1:1 with mineral spirits and apply it like danish oil – wipe on, wipe off. Wiping off prevents a film build, but it prevents other chemicals from soaking in and glue pops off. Recoat time I lightly scrape the top to remove the grungy stuff and wipe on wipe off.

View Kelly's profile

Kelly

2523 posts in 3503 days


#11 posted 12-01-2018 12:01 AM

OSU55, why would you not just wipe a light coat on and call it a day? Wiping it on and off is still going to build, but the mil thickness will, at most, just be a bit less than wiping a light coat on and walking away.

View OSU55's profile

OSU55

2450 posts in 2548 days


#12 posted 12-01-2018 03:36 AM

I should have added to let it sit for 10 min or so to soak in, keep it wet, like danish oil, then wipe off. Intent being not to build much film thickness, just like an oil finish but tougher.

View Fred Hargis's profile

Fred Hargis

5832 posts in 3052 days


#13 posted 12-01-2018 11:51 AM

OSU55 hit it right on the head about the varnishes. It’s important to keep the point about the world of woodworker’s separate from the commercial products. Another point worth reiterating is the book, the Flexner book should be required material in any hobbyist shop. A very close second would Jeff Jewitt’s book. They have pretty much the same info, but the Flexnor may be organized a little better for reading.

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

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