When to Thin Paint with Naphtha

Sign painters usually thin enamel paints with turpentine or mineral spirits. In this story, Jim Hingst explains when to use VM&P Naphtha as a thinner.

When a can of oil-based paint is brand new you can usually use it as is without any alteration. However, over time the paint will thicken and you will need to thin it. In most cases, sign makers and professional painters use turpentine or mineral spirits (also called “white spirits” by the Brits) as a thinner. In some special cases, you have another option.

When priming MDO, the accepted practice among the old timers is to thin a bulletin enamel 50:50 with either turpentine or mineral spirits. For this application, either solvent will work just fine. For finishing coats, these solvents are also generally preferred  because they evaporate at a slow enough rate for the paint to level out. That eliminates brush marks.

Sometimes you just don’t have the time. To speed up the drying time, veteran sign painter, Joe Balabuszko, recommends thinning the paint with VM&P Naphtha, which evaporates much faster than either turpentine or mineral spirits.

“When I was under the gun and had a lot of board to coat out,” Balabuszko says, “we would thin the paint for priming with naphtha. The primer coats would dry fast. Naphtha is much more volatile than mineral spirits so there would be no residual solvents to outgas and cause problems with the finish coats.”

Balabuszko says that VM&P Naphtha thins sign painting enamels to the perfect consistency for painting with a roller. "To achieve a finish that looked like it was sprayed on, we used 1/8" mohair rollers.”

Safety Note: VM&P Naphtha evaporates very quickly and is highly flammable. Use responsibly. Work in a well-ventilated area of your shop. Wear heavy-duty latex gloves, safety glasses and a respiratory mask.

Test, Don’t Guess.  Prior to using VM&P Naphtha with your brand of enamel, test it for compatibility.

Recommendation.  To keep your work tables looking good, cover them with RTape application tape when painting as shown below.

Conclusion. For most applications, either turpentine or mineral spirits are great choices for thinning oil-based paints. When you are pressed for time, consider VM&P Naphtha.  As a word of caution, keep in mind that different types of naphtha are on the market. They are not all the same thing. Some naphthas dry very slowly and will leave a residue. That’s not what you want to buy. Instead, look for the product labeled as VM&P Naphtha. The VM&P stands for “Varnish Manufacturing & Painters”.

About Jim Hingst: After fourteen years as Business Development Manager at RTape, Jim Hingst retired. He was involved in many facets of the company’s business, including marketing, sales, product development and technical service.

Hingst began his career 42 years ago in the graphic arts field creating and producing advertising and promotional materials for a large test equipment manufacturer.  Working for offset printers, large format screen printers, vinyl film manufacturers, and application tape companies, his experience included estimating, production planning, purchasing and production art, as well as sales and marketing. In his capacity as a salesman, Hingst was recognized with numerous sales achievement awards.

Drawing on his experience in production and as graphics installation subcontractor, Hingst provided the industry with practical advice, publishing more than 150 articles for  publications, such as  Signs Canada, SignCraft,  Signs of the Times, Screen Printing, Sign and Digital Graphics and  Sign Builder Illustrated. He also posted more than 325 stories on his blog (hingstssignpost.blogspot.com). In 2007 Hingst’s book, Vinyl Sign Techniques, was published.

© 2015 Jim Hingst