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I have heard on other threads and other forums not to use oil finishes. Others have said they work well and use them. Howard the other day said "Don't use one of the "Danish" or "hand rubbed" oil finishes". I want to know why ?
First of all "oil finish" can cover a huge range of things. Varnish, wiping varnish, different formulations of oil + resins+ dryers etc. Didn't some old time guitars use varnish ? Is the objection the oil part of some of the so called Danish oils. If so how much oil in a formulation is ok.
Another thing I wonder about is oils and softwoods. There are certain woods the don't do so well with oils. I am not familiar with spruce and oil. For those who do use "oils" do you first put on a shellac coat to keep the oil from making the spruce blotchy or is this not a problem.
I use a lot of oils in my furniture. It is my main finish for many years. I am familiar with a lot of products and they are quite different so what is the deal ?
Can someone splain all this to me ?
Thanks,
Link

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Cut to size.....Beat to fit.....Paint to match.

Oil finishes make great finishes on guitars, but like everything else they need using properly. I have used a type of oil finish on the last two guitars I've made (see the thread on my recent Cuban/redwood OOO) and also on the Torres copy 'La Lena', that I did short while ago. I also use oil finishes for most of the restoration work I do on historic 17th, 18th, and 19th century instruments. When I see how well the oil finishes on these old instruments have stood up to the centuries I wonder how good the Nitro will look in a couple of hundred years. On softwood just wipe a couple of coats of shellac over it first.

The stuff I use is not commecially available, as it's made for me by a bespoke violin varnish maker, but its closest equivalent would be Tru-oil which is a great finish. I just rub it out with rottenstone and oil.

One of the very top classical builders in Europe, he has built guitars for Julian Bream, will only use oil finish on his guitars because he says it is superior to anything else he has tried.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Very interesting comments Colin. I'm curious, what kind of applicator do you use to apply the oil (evenly), t-shirt material, foam brush etc....? Also what do you use to rub it out (steel wool, micro mesh etc...)?

I just finished applying Tru-Oil to my first build, and I found it difficult to apply the oil evenly with t-shirt material. It always looked streaky, and required a lot of rubbing between coats with 0000 steel wool. Thanks.

Ron M.

I wipe oil finishes on with linen cloth, though kitchen paper does just as well. I rub it out with a paste made from rottenstone and oil, again as has been used for centuries. Thes e finishes have to be applied very thinly, for each application, wipe some on, then wipe it off, this just leaves a very thin coat. T-shirt material is in my opinion wrong for oil finishes or French polishing, well washed old bed linen is much better.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

To clarify my very brief comment, it was about the "Danish" finishes, which often say "hand rubbed" on the can. These are mixes of oil based varnish (a chemically bonded mix of drying oil and a resin) with free oil (mostly linseed, sometimes tung), and usually lots of thinner. They soak in, don't dry hard, won't build a film easily, won't buff to a gloss, and can make softwoods look blotchy (sometimes hardwoods, too). The free oils can react badly with some tropical hardwoods. The negatives for these as guitar finish come from the free oils, and large amounts of thinner that soak them in.

Tru oil is a polymerized linseed (there are also polymerized tung oil finishes--Garrett Wade used to sell one made by Sutherland that worked well), and it will complete its polymerization when it dries, giving a good buffable film similar to a short oil varnish (a bonded mix of oil and resin that is long on resin and short on oil).

The mix and the type of resin, as well as the choice of oil control the characteristics of an oil based varnish. Generally less oil means a harder film, more oil a softer film that is more flexible. Behlin's Rockhard is an example of a short oil varnish. These finishes can work well on a guitar. They are said to have greater damping than nitro lacquer (which actually contains a lot of other resin, too. MacFaddens has more alkyd in it than it does nitrocellulose) or shellac, but I don't think that cashes out as any impaired acoustic performance if they are kept thin. A long oil varnish will not get hard enough to feel good on a guitar.

One more word: Flexner

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Bed linen, i going to try that next time. Thanks Colin.

Flexner?........You mean Bob Flexner? I have his book. Looks like you might have it too eh?

Another good book was written by Jeff Jewitt a while back...can't remember the name of it though...it's out in the shop too but I am too lazy to go out and get it.

BTW....Howard...I went to Woodcraft this morning to get some Tru Oil and they were out. Ordered it for me without a shipping charge though...

Here is a pic of some of the leftover's from my reproduction mission furniture days. I'll be using some of this on my builds.

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There is no difference between the man that thinks he can....and the man that thinks he cannot.

If you can find it, there's a good article in the old Catgut 'Journal', Series 3, Volume 6, Nov. '98, 'On the Acoustical Properties of Violin Varnish', by Martin Schleske. He applied the same amount of various finishes to cross grain spruce strips (which would show the largest effects) and compared them with controls that had been matched before the application of finish. Basically, what he found was:

1) all finishes add weight, of course,

2) some resins, and particularly nitro and shellac, actually added stiffness and reduced damping, compared with no finish,

3) plain oils can add a lot of weight and damping, and, as Howard pointed out, don't form a water proof film,

4) cooked oil-resin varnishes tended to add damping depending on the proportion of oil, but didn't soak in and did form good films.

I don't recall if he tested anything like 'Tru Oil'. Some of the stuff he used went by various German trade names, and I had to do some digging and get lucky to find out that he'd tested nitro at all.

On violins they may want some added damping, but we tend to dislike it on guitars. Oil will have less of an effect on the B&S than on the top, and I tend to avoid using varnish on the top these days. It's also hard to get anything much thinner than French polish, my top finish of choice.

Alan is correct that all finishes will add weight. I have done a number of tests though using French polish and oil finishes, the only ones I use, and properly applied I find that a good oil finish is no thicker than a French polish. However he is right that if you're not confident it may be better to finish the top in French polish and just the back and side/neck in oil.

And of course Howard is right to warn against the various oil finishes out there, my advice would be that if you don't have access to one of the boutique instrument finish makers then the only oil finish to use on your guitar would be Tru-oil, but remember to apply it very sparingly, very, very thin layers. Done properly there should be no need to use abrasives (same with French polish) until you want to produce the final lustre, this can be done simply with a dry finger as a burnisher on a very thin final coat. I do though usually rub it out with rottenstone in oil as is traditional.

A lot of German made lutes had no finish at all on their soundboard. I restored a Bruner some time ago that had never had any finish on the top, though the oil varnish on the bowl was in remarkable condition for its age. Here's a before and after restoration shot, still no finish on it of course.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Thanks all.

Colin have you ever tried Liberon star finishing oil ? It is from your side of the pond. I really like it. It is quite hard but it does penetrate a lot and that may make it unsuitable for guitars from what I have read here.
I would think a super thin shellac coat would help control the penetration though.
Link

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Cut to size.....Beat to fit.....Paint to match.

I asked this question to Michael Dresdner once. His reply was that it can soak in to and add density to the soundboard, so his inclination is to keep oil finishes away from spruce or other soft woods. He didn't have a problem with using it on the body or neck other than the fact that other modern choices are pretty easy to use and provide much better protection for the instrument.