Q: What are odorless mineral spirits (OMS)?
A: OMS is a safer substitute for mineral spirits or turpentine. It is petroleum distillate. There are two components to petroleum distillate: aromatic and aliphatic. The more toxic aromatic hydrocarbons have been reduced or removed, hence the milder odor. Since turpentine evaporates quicker than mineral spirits, high concentrations of aromatic components can become hazardous more quickly with turpentine than with mineral spirits. Turpentine is also more flammable than mineral spirits.
OMS is preferred over turpentine because of lower toxicity, lower volatility, and lower flammability. If you use a medium based on damar varnish, you must use turpentine to make your medium. If you add OMS to damar varnish, the resin will drop out of solution and cloud the medium. If you see a commercially prepared damar varnish or damar/turpentine medium that is cloudy, select another brand. Even if you use turpentine in your painting medium, use OMS for brush and studio clean up.
Q: How do I remove the metal seal on a can of Gamsol?
A: There are two methods:
Q: What is TLV?
A: TLV is an acronym for "threshold limit value", which is an OSHA measurement of how much solvent people can work around without adverse health effects. You can work with Gamsol OMS for three times longer than you can work with turpentine. Always request an Material Safety Data Sheet (MSDS) from the manufacturer of the solvent and check the TLV. Some brands of odorless mineral spirits have the same TLV as turpentine.
Q: Are all brands of OMS the same?
A: No. Some OMS brands cost $25.00 per gallon and some $10.00 per gallon. The less expensive are not 100% aliphatic solvent, which you can determine by the smell. Gamblin Gamsol is 100% aliphatic which means it contains no aromatic components. The price is not always a good indication of quality so ask for the MSDS from the manufacturer of the brand you are interested in using. The higher the TLV the better. Some brands of OMS have a TLV no better than turpentine!
For painters who want to test the purity of solvents, here is a simple test: Put one teaspoon of solvent in a clean shallow dish and let it evaporate. Turpentine will always leave a sticky residue, which is a good reason to limit its use to dissolving damar resin. The more impure the turpentine, the more residue it will leave. Impure mineral or odorless mineral spirits will leave a greasy residue. If all the solvent evaporates leaving no sticky or greasy residue then it is pure enough to use with oil paints.
Q: Which solvent do I use for brush & studio clean up?
A: We make Gamblin Galkyd painting mediums with 100% odorless mineral spirits (OMS). This is the mildest form of solvent that can dilute oil colors and thin Gamblin painting mediums. Regardless of the medium you choose, use odorless mineral spirits for brush and studio clean up.
Q: Are there any painting techniques for which alkyd resins are not a good choice?
A: Alkyd resins are more flexible than natural resins so if you want to break or scrape the paint film, we suggest you use natural resin varnishes thinned with turpentine and linseed oil. The usual recipe is 1/3 turpentine, 1/3 linseed oil, 1/3 damar varnish. Be sure to pour only the smallest amount of turpentine that you will need for the medium. Keep turpentine containers closed.
Q: What is the best system of ventilation for a studio?
A: Fresh air. Even when using OMS as your solvent, you should change the air in your studio once every day. Place a fan opposite the window. Place your easel perpendicular to the window. The purpose of this is to circulate the air between you and your painting. If you do not have a window, set the fan toward the back of your space facing the door. Open the door, turn the fan on high.