Query about oils for wood

[OldWood]

What's the difference between the various oils for woods - Danish, Tung, Teak, Finishing, etc. I've made a wooden item for Xmas presents and it could well get left out so if any finish an oil would be best but which one ?

Thanks
Rob

 

[Jonzjob]

What wood is it Rob?

 

[Blister]

What wood is it Rob?

Its oldwood , innit

 

[OldWood]

What wood is it Rob?

Its oldwood , innit

Pinch me line - d*** you Blister !! I knew I should have used my other alias for here which is in Gaelic

In this case it is ash, and here I've made a whole lot of holders for balls of garden twine for a craft fair - but the question was a general one.

Rob

 

[Jonzjob]

Well Rob, for ash bobbins (Daren't use a word like Balls in case I upset any politikz at the mo?) why not just leave them au nature (I think that I'm allowed to say that?) They ain't going to cause any problems and they will still be around when you and I are long gone mate :mrgreen: :mrgreen:

Just damp the finished surface a couple or three times and de-knib it each time and you aren't going to get a better finish..

 

[chipmunk]

Hi Rob,
To answer your question, in general I'd say that there are two types of oils - those drying (with solvent driers) and those non-drying.

Danish is a tung based oil but has driers in it. Finishing oil also has driers but teak-oil and tung oil don't tend to. Tung oil is a major ingredient in both Danish and Finishing oil. Other non-driers would be BLO, liquid paraffin, nut oils, olive, lemon oil, rapeseed etc etc.

For a shiny or satin finish, oils with driers IMHO are better/easier. Non-drying oils tend to be more matt. I also think that drying oils will provide a quicker finish than non-drying because they will be less mobile in the timber and so you don't need so many coats to get protection. But that means they don't penetrate as far into the timber.

The driers do what they say and encourage evaporation of the solvents in the oil. These are the ones that will spontaneously combust your rags if you leave them in a big heap after the job.

For items that may need some protection in-case they are left outside I'd go for a drying oil such as finishing oil (not as darkening on your ash as danish oil). If it were to be stored outside I'd go for a non-drying oil such as tung or teak oil and give it plenty of coats.

I like to use oil as a sanding lubricant. Your drying oils combined with sanding dust will create a really nice grain filler which will fill the open pores of the ash creating a really nice baby's bum smoothness ;-).

Dip the abrasive in the oil and use a brass brush to brush off any encrusted dust from the abrasive as you go, and keep re-oiling both the piece and the abrasive. It's a bit messy (cover your lathe bed and be prepared to wash your hands afterwards) but no dust to worry about and a fab finish.

HTH
Jon

 

[OldWood]

Jon - many thanks indeed; that is an excellent treatise on the subject and satisfied my ignorance on oil types perfectly.

I'm not sure that twine dispensers need to need to have a 'baby's bum' texture, so I will dispense with that sanding for this production project, but will bear it in mind for future.

Would you mind if I pass a copy of this to the webmaster of my club (Broxburn Woodcraft Club) for inclusion on the website as I've asked the question there and couldn't get the quality of answer you've given. Appropriate references will be given.

Rob

 

[chipmunk]

Hi Rob,
Be my guest. Glad it was of some use to you and hope it will be to others.

Rustins make the best Danish oil IMHO but for others I'd go for Chestnut every time. For liquid paraffin, the cheapest non-drying crystal-clear oil, try a farming outlet.

Jon

 

[OldWood]

Hi Rob,
Be my guest. Glad it was of some use to you and hope it will be to others.

Rustins make the best Danish oil IMHO but for others I'd go for Chestnut every time. For liquid paraffin, the cheapest non-drying crystal-clear oil, try a farming outlet.

Jon

Many Thanks, Jon - I went to the chemist for paraffin oil and was asked what is was for as it's no longer recommended for human use. They looked at me slightly oddly when I told them why. They had a couple of bottles left from old stock. I got a recommendation from this forum some time back for the initial coat for babies' rattles to protect the wood if the child proof coatng was penetrated. Useful to know there is still a source around.

Rob

 

[boysie39]

Jon, great bit of info. on the use of oils . Really very helpful, most of the pieces I have done I have used Liqued Parrifin on I would apply for sanding and after going thru the grits apply another coat leave dry for about 10 mins. and buff with a paper towel at about 500 RPMs.

I get a nice mat finish which I like. After some months I have applied a coat of Danish oil (Rustins) and have been pleased with the results.

 

[János]

Hello,

Dear Jon, there are flaws in what you have written about oils. Yes, you are right, there are two basic kinds of oils: drying oils and non-drying oils.
Some drying oils contain chemical dryers to fasten their curing, but not all.
Mineral oils are non-drying oils. Light machine oil and lemon oil are good examples of this group.
Some vegetable oils are drying oils. The drying characteristics of these depends on the actual chemical composition of the oils, and the amount and type of fatty acids in them. Linseed oil, walnut oil, tung oil are good examples of this group.
Some vegetable oils are non-drying oils, like rapeseed/colza oil, sunflower oil, or olive oil.
Some are half-drying, like poppyseed oil, or soy oil.
The drying properties of vegetable oils can be improved, the drying time shortened, by "boiling", a kind of heath treatment, pre-polymerization of the oil in fact. Boiled oils dry faster, and to glossier films. Boiled linseed oil, stand oil, boiled soy oil are good examples.

Dear Rob, ash is not a particularly wear resistant wood: it is prone to fungal attack and decay, so not the best choice for an outdoor project. Black locust/robinia, oak or chestnut would be much better. Finishing an item with drying oils adds some water repellent qualities, but gives no protection against fungi and rot. Treat your items with a solution of tannic acid, then give them a few coats of tung oil. High tannic acid content is the key factor behind the durability of oak, robinia etc.

Have a nice day,

János

 

[OldWood]

Hi Janos
I'm now beginning to wonder quite what can of worms I have opened; you don't say where you live but I guess from your name that you are abroad of the UK somewhere, and hope you understand the English saying about worms !

Thanks for your point about ash; the items I've made aren't intended for for leaving outside. The twine (garden string) will rot first and as that costs to replace, so the user will 'intend' always to return the holder and twine to the greenhouse (which it might be argued is only a little better than being outside!) - but to use another English proverb "The way to Hell is paved with good intentions"! Hence my consideration of an oil finish.

I'll keep your comments in mind for the next batch and use one of your recommended woods - learning in the passing why certain woods survive better outdoors than others; thanks. Could I add cedar and larch to that list ?
Rob

 

[chipmunk]

Hi Janos,
Thanks for putting me right about the natural oils and their drying properties. It's interesting that boiling can improve drying - I hadn't appreciated that.

I think Rob was looking for an oil to provide some protection if the ash was left outside almost by accident.

I don't think he was looking for full-blown outdoor protection.

Jon

 

[tekno.mage]

I'd recommend a hardwax oil for items that might get left outside. I've used on both Osmo oil and Chestnut hardwax oil finishes on a couple of stools that get used in an open-sided barn and are sometimes exposed to bad weather - two coats of hardwax oil has protected them very well with no staining or other damage from them being left out in the rain by mistake!

I personally would not use a dark-coloured oil (Danish or Tung) on ash - it makes it go a rather unpleasant shade of yellow-brown. I've not found the same problem with the hardwax oils, however.

 

[János]

Hello,

Dear Rob, I am Hungarian. Yes, you can add larch and some cedars to your list. And mulberry, elm, and European black pine (Pinus nigra), wenge, muiracatiara, padauk, bubinga, teak, cumaru for example. Generally speaking, woods with high tannic acid, volatile oil and resin content are more resistant to decay and rot, and to insect attacks.

Dear Jon, "boiling" means heating the oil in a closed vessel, closed off from air, so the oil starts to cross-link. The main problem with drying oil finishes is their low resistance to ultraviolet light, and the zero vapor barring ability they have. Adding large amounts of resins (colophony etc.) to them improves durability, and vapor blocking, but the resulting finish will be a varnish, not an oil finish. Marine or spar varnish is a solution of kopal resin and colophony in tung or boiled soy oil, for example.

Have a nice day,

János

 

[OldWood]

Bring this one back up to the top with a bit of feedback.

The story behind the original query was that a couple of us as 'progressing' turners decided to do a craft fair. I opted for a number of utility type items including the garden twine holders mentioned above. The craft fair wasn't as busy as we would have liked and we fell at one point to doing a crit. on our products. I was a bit gobsmacked when my twine holders failed due to rough finish - "better sanding required!". They had in fact been well sanded but the two coats of Danish oil I put onto the ash (colour was of minor importance here) have either raised the grain noticeably or perhaps dried dust onto the surface, but it would have needed to be some dust contamination to make the surface feel so positively rough.

Rob

 

[tekno.mage]

That sounds a bit odd. I've used a variety of oils on a variety of woods and never had a problem as you describe. I do apply my oil finishes off the lathe and in the house (ie away from sources of wood dust which might contaminate the drying surface) - so if you oiled yours in the workshop and left them to dry in there as well it's possible your rough surface could be contamination. I've never found an oil finish to raise wood grain significantly (as a water based lacquer will - and so needs cutting back between coats). Have you been able to cure the problem by cutting back with fine abrasive and applying another coat of oil?

 

[jpt]

Depending on the wood and oil that is not uncommon as the oil can raise the grain which will leave it feeling rough usually only after the first coat is applied. I always leave a means of rechucking the piece after the first coat so that I can denib it.

john