Sawdust on the Floor

I just finished reading an interesting article about altering the ageing process of cherry with chemicals. While I was interested in the content of the article, I couldn’t help but wonder why anyone would want to try to fool Mother Nature by trying to accelerate the aging processing of finishes applied to cherry.

OK, in retrospective I guess I could understand why a massive furniture manufacturer may want to change the time it takes for a piece of furniture made from cherry to achieve the desired aged cherry appearance.  For them time is money, and unfortunately in today’s economic environment, money or the bottom line is the Holy Grail.  But for the everyday non commercial woodworker, I  personally don’t see the reason.  But that is strictly my opinion.

One of the interesting things I gained from the article is exactly how dangerous it is to try to accelerate this normal aging process.  The most commonly used chemicals for this age acceleration processes are “Potassium Dichromate”, “Sodium Hydroxide” and “Potassium Permanganates”.  All three chemicals are known as corrosives, and according to their MSDS sheets are poisonous, and the use of gloves and goggles are mandatory.  Potassium Dichromate in particular is also listed as a known Carcinogenic. Carcinogenics are suspected as being a major cause of cancer.   In an industrial environment, maybe the use of these products could be done safely, but in the average shop the use of these chemical products could cause severe medical problems for you and your family.  This potential problem could be exacerbated if your shop happens to be in an attached garage or in your basement.   You may have on an approved respirator and goggles and other safety equipment on, but unless you also equip the rest of the family with the same equipment, they can be affected by the chemical fumes that can travel through the duct work in your home.

Another interesting fact that came out of the article was that the benefits of these chemicals are short lived. In fact over time, remember time is what we were trying to shorten, there can be significant color loss with the use of any of these three chemicals. Again, I don’t understand why anyone would want to take a chance using these dangerous chemicals for a short lived benefit.dark wood glue

In my shop, time is a fact of life.  It takes time for things to happen, and most of these things I cannot change no matter how hard I try.  The time it takes for wood to age is one of those items.  When I make a project using cherry, there are things I do different then when I make a project out of oak.   I will use rather than the convention white or yellow glues. Any glue squeeze out that is not cleaned up, will not show as badly.  When I work with oak, I normally will switch back to white or yellow glue.

My choice of finish for cherry is a combination of Linseed oil, Tung oil and Polyurethane.  This finish is applied in at least three steps.  After a finish sanding a 50/50 mixture of Linseed oil and Tung oil is applied to the finish. After being allowed to dry for several days, the finish is then sanded with wet/dry sand paper.  Linseed oil is used as a sanding medium.

The second coat is another mixture, this time the combination is a 50/50 mixture of Tung oil and Polyurethane.   This combination is applied to the project, allowed to dry for about 30 minutes before any excess that has not soaked into the wood is wiped off.  Just as with the first application, this coat is allowed to dry for several days. Then I sand this finish with more wet/dry sandpaper, linseed oil is again used as a sanding medium.

The third and often final coat is a coat of quality Polyurethane. I don’t use wet/dry sand paper at this stage.  Instead just a good sanding with a fine grit (300-400) paper is used.  Depending on how or where the project will be used, an additional layer of polyurethane maybe applied. 

And then, the project is moved into its final location and allowed to age naturally. Sure, I admit that my method doesn’t accelerate the aging process, in fact the only thing it has to do with time, is that it takes time. To me woodworking is a pleasurable thing to do, I’m not sure that I want to speed things up, just to make them look older. But if you want to use the any of these chemicals, please be sure that you take all of the proper safety precautions.

Being the type of guy who likes to know as much about a subject as I can, I started to do some research on what I’ve always considered a simple subject, good old plain everyday sandpaper. Only to find out that there is no such thing as plain simple sandpaper. In fact the more I read the more confused I became. One of the reasons for the confusion is that everyone who has access to the internet seems to have an opinion on what is and what isn’t the correct sandpaper to use.

I started out reading an article in “Fine Woodworking”, entitled “Sanding between coats for a flawless finish”. In the article the author talked about using Stearated sandpaper, as a sanding medium. While I had heard of the term, I wasn’t 100 % sure of the meaning, so I turned to the good old internet and goggled the word. And that’s where the confusion began. Not about the definition of the word, it’s a form of sandpaper that is classified as non-loading or self lubricating. The confusion was whether it’s a good or bad thing to use. Some experts claim that Stearated paper is the greatest thing since the invention of sliced bread, others claim that it’s the worst thing ever invented. The majority of the controversy is based on issues where “fisheyes” appear in the finished surface when Stearated paper is used.

While I was reading the posts discussing sandpaper pro’s and con’s, I can across references for both CAMI and FEPA sandpapers. Again because I’m somewhat obsessive, I had to look up those terms. It appears that American and European manufacturers can’t agree on terminology for sandpaper. The “Federation of European Producers of Abrasives” (FEPA) defines the aggressiveness of sandpaper based on a “P” scale, while The American “Coated Abrasive Manufacturers Index” simply lists the differences as “Grit”. Looking at a comparison chart between the two there actually appears to be very little difference between the two. A paper rated as 60 grit has particles that are 265 micrometers in diameter, while the FEPA P-60 has 269 Micrometers particles. Big deal, the difference is so small to the point of being of no consequences.
I did find some information that actually made sense; Sandpaper is available with three basic materials, Aluminum Oxide, Garnet and Silicon Carbide. Of the three, Aluminum Oxide is the most common paper, it last longer than Garnet or Silicon Carbide and is best used on bare woods. Garnet wears fast and is less aggressive then Aluminum Oxide. But has finer scratch patterns, making it a better choice for finish work. Silicon Carbide is harder then Aluminum Oxide, but wears fast. Silicon Carbide can be used both as a wet or dry medium, and is a good choice for between coats sanding.

While I’m still confused about what type of paper to use, I do concur with the idea that it is imperative that any finish you apply must be sanded between coats.
I guess the next time I go to the store to buy “Sand paper”, I will have a lot more to think about. More than just what grit paper I need.