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I initially sealed with Rustins DO thinned 20% with white spirit before filling pores using RDO, slopped on inside and out liberally and for a long time. After this was dry enough pore filling was accomplished by wet sanding and adding some gloop Mr Waghorn gave me years ago (rottenstone is commonly used). Surface when dry then cut back almost to bare wood and finish coats applied as per my previous post. Penetration into the wood, typical of this kind of finish, is actually pretty poor. The finish tacks and hardens in good walnut before any meaningful penetration occurs. I suppose if a stock is made from soft, porous (shitful) walnut then penetration will be more impressive. I prefer good stock wood however. I reckon from experience, if you want one of these finishes to penetrate deeply, try vac bagging or soaking the stock in a pressure vessel under a partial vaccum to suck the finish in before it starts to harden. If you doubt this, scrape back your finish and see just how quickly raw wood appears. If the finish or sealer is thinner and hardens slowly, then of course it'll penetrate a bit deeper. Or use a compatible oil that dries very slowly as a base coat to nourish the wood, provided the pore filling and finish coats will harden and bond with it.

I suppose, at the end of the day, I'm just not a fan of thick, built up coatings on stocks no matter how nicely done they are. IMO for a built up film finish, for me Tru Oil is far easier to apply than Rustins, and a bit tougher. In the context of this thread, which was supposed to be about traditional Linseed stock finishes, Rustins is about as much an "oil" finish as Tru Oil. Applied in thicker coatings, it looks almost identical to Tru Oil. Pretty garish unless get back.

If you looks at the Rustins site under Our Products, they make a clear distinction between Indoor Wood Finishes and Outdoor Wood Finishes that they offer. Rustins Danish oil is clearly listed as an indoor product, not an outdoor one. Whilst the advertising blurb lists that the product can be used on outdoor woodwork, I think the manufacturers classification speaks volumes. If it truly held up to outdoor use, they'd be promoting it e.g. for wooden boat use. Rustins Product Data Sheet also states nothing at all about exterior woodwork compatibility, only indoor use. That ought to tell folk something. As far as goodies in the brew, RDO Info and SDS sheet states it has some vegetable oil in it, mainly Tung oil, but it is modified with synthetic resins and driers (looks like cobalt driers), 44.170% petroleum based thinners with a dash of MEK for good measure.

Like most of it's brethren of Scandinavian, Teak, Danish etc "oils"........there is some oil in there somewhere, but essentially they are "modern synthetic varnishes" of one type or another. Alkyd, phenolic, urethane etc.

Decades-old technology: when a natural vegetable oil is heated with a chosen synthetic resin (eg alkyd, urethane, phenolic) the oil and synthetic resins combine to produce a new product. Essentially, modern varnishes. These ratios are manipulated by industrial chemists to vary the performance of the varnish. Typically "long oil" varnishes have 50-100 gallons of oil for every 100 pounds of synthetic resin mixed with it. These are the greatest oil content. Medium oil varnishes have 12-40 gallons of oil per 100 lb resin, and short oil varnishes less again. Spar varnishes are long oil varnishes, without added driers they are very slow to dry but are flexible, although fairly soft. The resin used is important, particularly for outdoor use. Oils used also affect appearance and performance. The "varnish" is then thinned, most often with petrochemical thinners, and often metallic driers are used so the brew hardens in a timely fashion. Nearly all of the commercially available "oil" finishes fall into this category. The huge VOC content of these finish types is becoming an increasing problem with various govt regulations for such.

http://antiquerestorers.com/Articles/SAL/varnish.htm

I think the original intent of this thread was to demonstrate an exploration of more traditional varnishes, ie those which do not use synthetic resins, metallic driers, and petrochemical thinners. When it comes to traditional varnishes, there are two basic categories, spirit based and oil based. Whilst many vintage guns have been finishes originally with finishes that contained some metallic dryers, it's also true that many were not. Some fine finishes can be built up with traditional varnishes, and in my experience their performance in the field can equal or exceed many of the modern products all things considered. I've got nothing against either type of finish (modern vs traditional or anything in between), but most off the shelf products are just NOT genuine oil finishes or anything like it, in my eyes.