Superretrodyne wrote:
Jim,
I'm glad to hear that worked well for you. I will try it on a few books.
Arran,
This is a delayed response as I was up in your neighborhood at the Olympic Peninsula with no means of communication. I wasn't expecting the Sitka spruce to be so large.
Shellac is wonderful. I'm sitting at a French polished desk. There is a piece of birdseye maple on the desk I just sprayed a coat of Zinser on for my wife to take a look at for use in the renovated kitchen.
Yes, something may have been done to the case to help it survive. Do you really think the manufacturer was trying to insure it would last for generations? It's just a consumer item. After 80 years, entropy has almost always won. The inside of a case is not finely finished like the outer case. Any shellac coating it was given 80 years ago probably was permeable from the beginning. Temperature and humidity changes, unless it was kept under museum conditions, the shellac insignificant in a few years. Shellac is a technically a thermoplastic, attached to the wood by adhesion. A standard "tape test" on a new shellac surface will probably remove 5% of the finish. Shellac is the most fragile finish. It flakes, and alligators. Humidity, temperature, water, alcohol, pH changes, and many other agents easily breach whatever seal shellac may have originally provided. Most gas penetration is through the end grain, which is generally neglected anyway. Wood structure is like a straw. You can actually blow through a piece of seasoned red oak. Microbial agents work from the inside to deconstruct cell walls in wood. A small drop of water easily tests the permeability of a surface. If it still has surface tension after 5 minutes, the finish is sound. Otherwise, it really provides no protection. There are also several ways the long term life of shellac can be compromised before it is even applied.
An original French polish is the best form of a shellac finish. It takes about 50 coats originally and then must be renewed, frequently, if it as an object that is actually used. Professionally used French violin bows are generally renewed every time they are rehaired, which is at least annually. A luthier who practices French polishing over the original varnish will renew the shellac on every visit. My daughter's 1769 Austrian is redone twice a year. My desk is in need of a going over. I have a massive late 19th century French china cabinet that horribly failed a shipper's version of a tape test. It lost 100% of its finish wherever packing material was taped to it.
So, my advice remains, if it smells, an easy way to hide it is to seal over it.
John
John;
You are really splitting hairs, the point I was trying to make was that the insides of any radio cabinet that I have owned was not raw nor untreated wood, shellac was only one of several coatings that may, or may not have been used on the inside, a dab of alcohol would quickly answer that question. There are also different grades of shellac, different cuts (ratio between pounds of shellac used per gallon of alcohol) and different colours, all with different characteristics. Like for instance, 78 rpm records were often mounded from shellac, they do not often warp, nor do they break down easily, even in humid environments, so clearly the mixture used is a lot more durable then white shellac.
In Zenith cabinets they used a dark blue paint, in RCA sets it was often silver paint, sometimes a dark brown, what the chemical nature was of these is unknown. Hide glue seems a likely candidate for a sealer, it was cheap and readily available in any cabinet shop. Casein was another popular substance used back in those days, along with some early man made substances. Again, the point being is that the insides of the majority of these cabinets was sealed with something, and it does not simply disappear, which means that odors would not necessarily penetrate the wood and could largely be removed by cleaning.
Regards
Arran