Popular Woodworking 2007-12 № 166, страница 62

Thinning varnish. Any petroleum distillate or turpentine can be used to thin wax, oil or varnish, but mineral spirits (paint thinner) is best. It gives the finish time to level and is less expensive and has less unpleasant odor than turpentine.

greasy or waxy surfaces. Mineral spirits is better for thinning oils, varnishes (including polyurethane varnish) and oil-based paints because it leaves more time for the coating to level after brushing.

Naphtha is a stronger solvent than mineral spirits, but this is rarely significant in wood finishing. Mineral spirits is strong enough for any normal operation.

To better place turpentine among the petroleum distillates, think of it as having the solvent strength of naphtha but the evaporation rate and oiliness of mineral spirits. I don't know of any situation in wood finishing where this is important.

The nickname for mineral spirits is "paint thinner." Back in the early days of mineral spirits, before World War II, all paints were oil-based. So there was only one thinner for paint. The nickname made sense.

Today, with water-based paints and finishes in wide use, the name could be confusing to beginners. Paint thinner is used only with oil-based paints and finishes.

It's important to emphasize that mineral spirits and paint thinner are the same thing. Amazingly, there are manufacturers who try to trick you into paying more by labeling their containers "pure" mineral spirits and charging more.

The common naphtha available in paint stores is VM&P Naphtha. VM&P stands for "varnish makers and painters." Stronger and faster evaporating naphthas exist, but these are rarely sold to the general public.

Toluene and Xylene

Toluene, nicknamed "toluol," and xylene, nicknamed "xylol," are the strong, smelly, fast

Cleaning oily surfaces. Naphtha is usually better than mineral spirits for cleaning oily or waxy surfaces (including crayon marks) because it evaporates much faster. Naphtha also has more solvent strength than mineral spirits, which is sometimes helpful on old waxed surfaces like this one.

evaporating and "dry" parts of mineral spirits and naphtha. These solvents are removed from mineral spirits and naphtha at refineries and sold separately as cleaners, and also as solvents for some high-performance spray finishes such as conversion varnish. Toluene and xylene are very effective as cleaners, but I find naphtha adequate for almost all situations.

Toluene evaporates a little more quickly than xylene, but this is significant only when using the solvent as a thinner.

The problem with these two solvents is that they are relatively toxic. They will affect your nervous system causing irritability and drunkenness, and in large doses could cause serious health problems. You should never use them in any sizeable quantity in a room without good exhaust.

One very interesting use for toluene and xylene is to soften latex paint. Using a dampened cloth (and solvent-resistant gloves) you can easily remove latex paint that has spattered off a paint roller, or even a full coat of

latex paint, from any finish except water-based finish, without causing any damage to the underlying finish. In fact, the products sold specifically to do this, "Oops!" and "Goof-Off," are principally xylene.

Because white and yellow glues are the same chemistry as latex paint, you can also use toluene or xylene to soften and scrub these glues from wood when you have glue seepage or fingerprints that you didn't fully remove during sanding. You will need to use a toothbrush or soft brass wire brush to get the glue out of the pores.

Odorless Mineral Spirits

The mineral spirits left after the toluene and xylene are removed is sold as "odorless" mineral spirits. When understood this way, it's obvious that odorless mineral spirits is a weaker solvent than regular mineral spirits. But I've never found this to be a problem. It still appears to be strong enough to thin all common oils, varnishes and oil paints.

The disadvantage of odorless mineral spirits, of course, is that it is considerably more expensive because of the extra steps necessary to produce it. You may find the extra expense worth it, however, just to avoid the unpleasant odor of regular mineral spirits.

Turpentine Substitutes

The so-called turpentine substitutes are an interesting breed. My first question when I talk to the companies that produce them is, "Isn't that the role of mineral spirits?" (One company spokesman, identified as the "chemist," explained that these products were necessary because of all the protests against cutting down trees to make turpentine! Of course, trees aren't cut down; the sap is drained.)

surfaces except water-based finishes. The com- Thinning shellac. Denatured alcohol is the best mercialproducts "Oops!" and "Goof Off" are solvent for thinning shellac. It is much less toxic based on xylene and sold for this purpose. than methanol.

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