Shellac and Boiled Linseed Oil

B

briyon

Well-known member
I am about to finish a mahogany Newport Tea Table and have a question about the finish.  My plan was to finish in just shellac but I believe that Al Breed said he finished his by starting with a coat of BLO and then putting shellac over the top.  I took his Newport Carving class and I believe he said he uses the BLO to give the piece depth.  I have also heard that you don't want to use any oil based products under shellac.  Can anyone help with information/experience with this type of finish?

Thanks,

Brian
 
No need to question anything Al says.  He is a true period furniture master / diety. He is the best of the best.  He is correct that it does give it some depth and it makes the finish  a little darker over time.  You absolutely can use oil based products under shellac.  I do it all the time.  Shellac goes over most types of products without a problem. Use dewaxed shellac.  What you heard was wrong and you never need to question anything Al B tells you.  

Heck, I have been watching this forum intermittently since the start of the SAPFM and have only begun to check in several times a day now since Al started posting.  I wouldnt miss an opportunity to learn anything I can from him.
 
Al is the best and most knowledgeable on period furniture making that I know. 

I use pure tung oil sometimes in lieu of BLO.  Some people say BLO never really dries.  If that is a concern, then add a little Japan drier.

Dewaxed shellac can go over on under nearly all known finished.  It is considered a great barrier between finishes.

Good luck.

Ken
 
Scott- Bless you my son.
I do put oil under shellac, and when I used to work with the old Italian guys in Boston I watched them French polish over raw linseed, but these guys were literally old pros and I would never try it myself. I do think the oil brings the wood to life, and when it comes to a shellac finish I can get by, but if I need a French polish I have a finisher who does it for me.
The true deity of shellacdom is, by the way, Don Williams at the Smithsonian, with others scattered about here and there. Finishing is an art unto itself, a whole different discipline, and in that light I consider myself a competent hack.
Thank you for your compliments, Scott, but take all info with a degree of skepticism, especially these days where the only prerequisite for the label "expert" can be the ego of said "expert".-Al
 
I beg to differ on this one,and I mean no disrespect but although BLO was used regularly in the past,history has also shown a problem resulting from it.As it ages it turns black.Now it may be alright to use it on things you build [I wouldn't] don't use it on historic restorations.I would also be careful putting shellac over modern finishes[addhesion concerns].Also using shellac with wax in it ,or shellac over wax, will change the hardness of the finish. Dewaxed shellac is harder/less elastic than waxed shellac, both have there place to be used.  Randy
 
I would agree with Randy. Though I have far less experience than he has in finishing. I wondered about this BLO under shellac makes the wood "POP" so I made a sample. I can see no difference in the color or depth of finish. Maybe I need to make another sample. If you have a side by side sample of BLO under shellac and just straight shellac on the same board maybe you could let us know what you see.
Thank you Al for your response to Scott, I thought he was gushing just a bit. I am glad he had a good experience with you but I assume you are human. It would be lonely for you were you not.
Mike
 
Randy- I agree with you about BLO on antique stuff, no conservator today would use it on period pieces. I'm hoping for some darkening on my new stuff and time will tell how dark it eventually gets.-Al
 
I, like Mike have done experiments with pre-oiling the wood before the shellac or alkyd varnish was applied. What I found was the pre-oiled wood had more depth after the first coat. However, as the finishing progressed the difference disappeared and when the finishing was finished, I could not see any difference. If I remember correctly FWW did this test a few years ago with the same results.
As to using the oil to darken the wood a bit I use the various types of shellac to accomplish this. The grades all have a different tint and using them to steer the end color to your satisfaction works well.
I have a white maple board that I have sectioned off and then wiped a 3" wide stripe of the 5 grades of shellac I have on it. I can easily have it on hand and if I want a little or a lot of orange,brown, green ect. I look at the sample board and pick the one that looks like it will add the color I want. When the color is right I switch to Super Blond if more coats are needed.
John
 
Something I can actually comment on.

The 'depth' of a finish is dependent upon the optical clarity of the finish material. Oil looks good at first, but dulls as the material solidifies and loses it's ability to reflect light from the structure of the wood. Clear hard film finishes transmit with a higher level of optical clarity (it's called an index or something like that) dependent upon the type of finish and the amount of foreign material held within the substance. The tint of the finish also changes its ability to transmit light.

All we are seeing is the cellular structure of the wood reflecting light through the finish. Some woods in the raw state reflect light better than others. Resinous woods tend to look better in the raw state as the resins reflect light better than plain old wood cellulose. And so on.

It's all a matter of the physics of optics. Which is to say that I've just exhausted my entire memory of physics in this answer.

As an aside, for a forum that contains a fairly sparse array of posts, at least compared to many of the woodworking forums, the contents here is excellent.

Gary
 
I am somewhat reluctant to leap in to this discussion, but after reading Gary's little missive I feel somewhat more confident. Organic oils oxidize very rapidly. That wonderful depth you see for a day or two quickly diminishes within weeks. Oils, being alkyds, are readily degraded by washing with soaps (like dissolves like). On the other hand there is some strength to the argument that shellac bonds to anything. This is obviously true, however it will follow a puddle wherever it goes. Moving on from this to a topic that is very dear to me, I would like to suggest that when applying shellac using the French polishing method, it is necessary to accommodate the type of wood you are finishing. While it is absolutely necessary to apply oil to mahogany, the application of oil to cherry or maple will bring about an entirely different effect, universally a disastrous one. The application of oils when using shellac can also be problematic. The overuse of oil provides a substrate for the fillers to be bouyed in at first, but as they are absorbed by the wood and oxidize over time the finish we initially create is pulled in to the pores as it follows the oils.
 
Frangallo:

Far be it from me to opine on topics I know of primarily from my personal woodworking and from old musty texts. To wait for my word to be evident afore setting your own prose to print is naught but a foolhardy venture.

I'm here to listen and learn from those who put sharp edge to wood. On occasion, to kibitz and make comment from those texts on my shelves. A library type by training and inclination, I tend to accumulate knowledge, not always knowing if or when it will be of use.

Which said, I am shocked at the current prices some of these 20th C classics are bringing. The Newport book is going for how much? I tend to have my head stuck in early 20th C, most 19th C and some 18th C titles. I should read the other shelves more often.

Gary
 
All delights are vain. But that most vain which with pain purchased, doth inherit pain. As painfully to pore upon a book. To seek the light of truth while truth the while doth falsely blind the eyesight of his look. Light, seeking light, doth light of light beguile. So e'er you find where light in darkness lies, your light grows dark by losing of your eyes. Study me how to please the eye indeed by fixing it upon a fairer eye who, dazzling so, that eye shall by his heed and give him light that it was blinded by. Study is like the heaven's glorious sun that will not be deep searched by saucy looks. Small have continuous plodders ever won save base authority from others books. These earthly godfathers of heavens lights that give a name to every fix'ed star have no more profit from their starry nights than those that walk and wot not what they are. Too much to know is to know naught but fame, and every godfather can give a name.
                                                    W.S. Love's Labours Lost-- Act 1 Scene 1
 
A few comments folks, from a person with a background in chemistry.

Linseed oil never really dries:  This is not actually correct when talking about boiled linseed oil, though it does depend on your definition of "dry".  Back in the day, white lead (lead oxide) was added to hot linseed oil to get it to dissolve.  The lead acts as a catalyst to cross-link and oxidize the linseed oil.  This practice was continued up until the 1970's, when a ban on lead in paint caused a change to cobalt salts in place of the lead oxide.  The cobalt salts do the same thing - the catalyze the cross-linking and oxidation of linseed oil.  Where this saying comes from is in oil paintings - the linseed oil that is used to thin oil paints and as a carrier for pigments is usually raw linseed oil, and it hardens much, much more slowly than the boiled kind.  In some cases, it's decades.  Neverthless, I can assure everyone that the linseed oil in one of Van De Meer's paintings has long ago hardened like granite.

About linseed oil under a clear finish - one of the reasons that curled woods like maple "pop" when you oil them is you are replacing the air in the cut cells at the surface of the wood with oil, which has a different refractive index.  However, most clear finishes will look just about the same after a few coats as will linseed oil, and the reason is that the finishes either contain oil as a substantial component (alkyd and phenolic varnishes, oil-based polyurethanes, and the like) or have oil-like refractive properties (i.e., shellac and laquer).  All of these finishes have a very low surface tension, and will readily replace the air in the cut cells of the wood just as will linseed oil.  Since these finishes will do the same thing as linseed oil (replace the air in the cells of the wood), it makes sense that you would not notice a difference after a few coats of these finishes on either a native wood surface or an oiled one.

However, there is a difference between some water-based finishes and the oil-based ones.  Depending on the exact finish formulation, the water in them may retain a high fraction of its original surface tension, and it may not replace the air in the cut cells of the wood as an oil would.  Moreover, these finishes will actually hydrate the cells of the wood at the surface, which causes them to swell shut.  I've actually seen the curl in a piece of curly maple dang near dissappear when I used a water-based polyurethane on it (don't ask - it was a cutomer demand.  I poured the rest out on my deck as a sacrificial coat of finish where appearance didn't matter).

Finally, with regards to french polishing, the linseed oil is a necessary accoutrement.  Without it, the rubbing pad will not glide over the surface as it should.  Instead, it will stick and grab, leaving behind undesirable marks.  You can, by the way, use mineral oil for this purpose, though because it will not dray, you must remove it in the "spiriting off" phase.
 
David- That was a great explanation and makes sense to me. Can I please keep using oil? Maybe it's that woodshoppy aroma that I just wouldn't feel right without-Al
 
Excellent explanation of linseed oil.

By chance,  I'm in the middle of prepping a copy of The Painter, Gilder and Varnishers' Companion, 1850, Henry Carey Baird (publishers) for re-issue. A brief quote:

"Nut oil and Linseed oil... before employing them in colouring, to give them a drying quality... take three parts of white vitriol (zinc sulfate), and twelve parts of litharge (lead oxide), and let them be reduced to as fine a powder as possible, then mix them with thirty two parts nut or linseed oil (and so on)"

There is an entire chapter on the ills that befell painters, gilders and varnishers as a result of the lovely products they worked with. Now isn't that pleasant?

Gary
 
By the way, guys.  Konrad Sauer posted a fairly neat description of how he French Polishes those plane totes and knobs to a mirror finish on his blog.  It's quite interesting.

One note to any newbies reading this thread - boiled linseed oil, tung oil, and varnishes that contain oil (which is most of them) are dangerous when the rag that's used to wipe them on is casually thrown into the trash.  The "drying" part is actually oxidation, and just like the more rapid oxidation we're all familiar with in the fireplace, the process generates heat.  The wadded-up rag in the trash can easily and quickly cause a shop fire.

To safely handle the finish-soaked rags, spread them out on a surface to let the finish cure and then throw them away, or put them in a bucket of water.
 
Something that nags is the advice to throw away oiled rags. Why can't you launder them and reuse?

Pam
 
You can - however, it may excessively contaminate your washing machine, so you might have to do it by hand.  I've laundered the oil-soaked rags before, but I concluded that the necessary detergent and amount of hot water probably didn't save me any money and definitely didn't help the environment out any.
 
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