Peter:
Faced with an old piece with a damaged finish, how do you figure out what the finish is, and how to approach repair? I guess you could test for shellac with alchhol, but how about other stuff?
For example, the cracked finish in the plane tote and know we already talked about, OR the top of a glass front bookcase that has a lot od damage due to old coffe cup rings, OR an old oak player piano with a badly alligatored finish.
Edited 4/7/2007 10:42 am ET by Joe Sullivan
Replies
Hi Joe,
When analyzing a finish one of the main factors is the age. We know that lacquer became the production finish of choice by the 20's and 30's. You can test for lacquer using lacquer thinner in an inconspicuous spot as it will soften it the same way alcohol softens shellac.
There is also an acid I've seen applied to a lacquer surface and it would turn purple within a second or two identifying it.( I don't remember what the acid is though)
The others mentioned could be a fixed oil varnish. These are made with a drying oil (tung or linseed) and had resins such as amber and copal in the better grades and colophony (rosin) in the cheaper grades.
The other that was still used was the spirit varnish IE; shellac with various resins added ( mastic, soft copals, Venice turpentine, etc.)
The oil varnish won't respond to the alcohol treatment while the spirit obviously will.
Of course there is always the good possibility a piece was continually rubbed by what is often referred to as the "witches brew" of linseed oil and turpentine. This produces a cross linked crud that is the bane to restorers and conservators.
A conservator would turn to microscopy for an analysis. This would entail encasing a small piece of finish in an acrylic cube, cutting it on a bias, magnifying it and hit it with ultra violet light.
Shellac will fluoresce orange while the plant resins will glow white. A modern finish will show no fluorescence at all.
It would be interesting if you had access to a lab. Do you?
Peter
Peter:
Very interesting. I have limited access to a very good conservation lab, but it is a couple huindred miles away and so not too convenient.
Have had experience with black light on textiles and paintings represented as being "period." In those cases, you usually just look for significant differences in fluorencence in order to determine whether modern rework or alteration is present. It can be quite striking. Now I will have to go shine black light on furniture and see what glows back at me. Admittedly that is not the same as encasing, cutting and magnifyng, but who knows?
So, as a hypothetical followup, suppose you have a piece of furniture before you to be restored. How important is it to identify and match the original finish?
Joe
Joe,
That's a good and philosophical question. I would again turn to the age of the piece.
However, that said, there are a few questions I ask. What is expected of the piece we are restoring. What are the expectations of the client?
The obvious example would be a dining table. If it is a period piece and the finish is in need of attention what approach is taken? If the client expects it to have a trouble free modern coating, should we acquiesce and spray it with lacquer? After all it's a reversible finish. Should I brush a varnish on instead, which is not reversible?Should it be French polished or possibly re-coated with a copolymer such as B-72?
The thought of a French polished dining table will be scoffed at by many. It's not alcohol proof, it's not heat resistant are but a few of the valid arguments. Yet it's done to period furniture by many restorers and conservators. All the coating takes is a modicum of care. Have you ever seen people jump when something as benign as water gets spilled during a dinner? Paper towels and napkins are flying to the rescue.
Let's zero in on the table and suggest it's a Federal piece. What was the finishers original intent? It could possibly have been rubbed with an oil and waxed or , especially in the large manufacturing areas such as Boston, New York or Philadelphia, the finish could have been the fore mentioned spirit varnish. Faced with these choices I would suggest the client went with the latter. Knowing shellacs adhesion properties would make it easy to restore a surface. If a modern finish was demanded you could possibly re-coat with lacquer using shellac as the barrier coat first. For a modern coating in this case I would opt for lacquer instead of a varnish due to it's reversibility.
Finishes became more durable as the industrial revolution progressed and many Victorian pieces retain their coatings intact. They may show strong signs of crazing but remain sound otherwise. However, in many circles this furniture is dismissed with a who cares attitude. Should we arbitrarily strip it and re-coat or save it? If it's stripped should we be concerned with a reversibility issue when it gets refinished?
To sum it up, when working with period furniture I always take a "first do no harm" attitude. I'll do my best to identify the coating.
But that raises another issue. How old is the coating. After all, at the turn of the century many pieces were scraped down and had a new coating applied. It may have started to develop a secondary patina by now, but it certainly is not original.
"Original finishes" are exceedingly rare. There may well be traces that are identified in a lab, but on the surface, hardly ever. They just didn't stand the test of time.
I'm sorry if this got long winded. I love furniture and the study of it as a decorative art. I'll leave you with this; we never really own furniture, we're just care takers for the next generation. What do you want to leave behind?
Peter
Excellent answer, and one I will thinkcarefully about. You would get on well with the museum and collector crowd I hang around with , BTW.
Joe
Joe- let me chime in here...
as for figuring out what an old finish is, there is a book, which was years ago advertised in FWW called "the Furniture Doctor" and while it may be out of print, it could likely be found at yer local library, and if they don't have it, they could likely get it through an interlibrary loan. Author is George Grotz ; Lib of Cngress # is 62-7640
Worth checking out.
Eric
Sounds good.
J
cowtown,
Is there anything in particular for reference in there? I've read it at one time and know(think) I have a copy around somewhere.
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