FINISHING SECRETS . . .
13. Addenda and FAQs

    These articles have been in a continuous revision during the years since they were first written in 1996 and 1997. In December, 2001, I realized that they were as complete as they were ever going to be, and it was time to stop making changes, corrections, and additions. This was not to be, and there were still questions from readers, presentations, and newsgroups that were of importance to the subject of finishing. This addendum is written to correct those omissions, answer the frequently asked questions, and provide new information. These topics are not in any order of importance or content.

Shelf life of mixed shellac and shellac flakes
    While shellac flakes do have a long shelf life, it is not infinite, as stated in Article 9 of "Finishing Secrets." Shellac flakes will deteriorate over a time of several years and exposure to high temperatures, light, and moisture in a process called "esterification." While they will still have the same color and appearance, they will no longer easily dissolve in alcohol. If the old flakes form a mass in the bottom of the container rather than be dissolved in the alcohol, you will know that they are too old. How long does this take? I have 10-year old flakes that have reached an age where they will only partly dissolve in the alcohol, so it is time to throw them away.

Which finish do I prefer, and why?
    The answer to this question is that it usually doesn't matter what finish is used, so long as the wood was properly sanded and prepared prior to its application. Some reasons for using a particular finish are discussed in the individual sections. However, there are applications where a specific finish is preferred.
    There is no environment more severe than that of the gallery. The lighting in most galleries is very bright full-spectrum fluorescent, and on for 24-hours a day, the air is too dry to be suitable for wood, displays are placed in bright sunlight, the pieces are handled often and subjected to acidic body oils, fingernails and rings, they are sometimes dropped, and the wood will be subjected to water droplets if there is a waterfall art within 20-feet of it. This environment calls for the best protection that can be put on the wood, also one that can be easily repaired, and that is an oil/varnish.
    This same durability is the reason that I use an oil/varnish on most of my large pieces.

Since lacquers are so difficult to apply, why would anyone want to use them?
    Yes, lacquer can be a difficult finish, but it will be less so if we wait for the proper conditions before its application. There is nothing better than lacquer to accent that special piece of wood with a spectacular grain picture. For this it is worth the wait and the effort.

Why am I such an advocate for tung oil?
    Most finishing texts say there is no difference between what oils are used.
    It may be true that there is little difference in the short term or when used on a table top that will spend most of its life covered with a cloth. However, I believe that whoever receives something that I have turned and finished is entitled to expect that the finish will last for many years, without deterioration or change in color when placed in the exposure and handling of a normal household environment. It is my experience that Tung Oil is the only oil that meets these criteria.

Aren't the "traditional" finishes and solvents that I use more harmful than waterborne finishes?
    There is a popular misconception that, because they use water in their composition and are EPA and State approved, these finishes are as safe as using water. Not true!!! These new finishes are approved as being less harmful to the environment because they contain fewer, or none, of the volatile hydrocarbons. However, many are more harmful to their user than the traditional finishes.

Is there such as thing as a durable and "quick" finish?
    No. The problem here is that "quick" and "durable" are not mutually available. As an example, shellac can be a very hard and durable finish, but it will take several months for the finish to fully cure and reach its ultimate hardness. On the other hand a shellac based friction polish may be fast, but it will not have the hardness required for a durable finish, and the waxes it contains may hasten its deterioration over time.
    The closest that I can come to meeting the quick and durable finish is the wipe-on application of Deft that is described in Article 3. Even that is not very fast and it isn't very durable.

What finish can be put over mineral oil?
    This question has been around for many years. There are those who say nothing can be put over mineral oil, and there are those who say that they do it all the time. As we would expect, the answer is somewhere in between.
    Mineral oil is a petroleum product. In the simplest of terms, it could be described as highly refined and edible lubricating oil. As such, it does not dry when it is applied to the wood. Mineral oil is soluble in all petroleum based thinners and turpentine, and any finish that uses these same solvents can be put over it. Lacquer, shellac, varnish, and drying oils will absorb any mineral oil that is already in the wood into the new finish, and there will be no adhesion problems.
    However, there is a penalty. The mineral oil acts as a "plasticiser", and the new mixture will cure to a softer finish than if it were used alone over bare wood. How much softer will depend on how much mineral oil is present. And, the softer finish will deteriorate with age much faster than if it were applied over bare wood.
    If you are willing to accept this compromise, then the answer is that, yes, a finish can be applied over mineral oil.

 
 

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