Essential Solvents for Sign Painters

Here’s detailed information on solvents used in sign painting. Solvents described include Pure Gum Turpentine, Mineral Spirits, Lacquer Thinner, Toluene, VM&P Naphtha and Xylene. Hingst extensively covers solvent safety, the new safety data sheets and the HazCom2012 standards. 

A solvent is any liquid that can dissolve another substance. That’s a fairly broad range that includes everything from acetone to water. Working with solvents is unavoidable for sign painters and most artists. Unless the solvent is water, all solvents are hazardous and nearly all are flammable. Even sweet smelling d-limonene is toxic. Yet, if you practice solvent safety you can limit the risk of these chemicals being inhaled or absorbed through your skin. Careless use of solvents can result in damage to your central nervous system, liver, kidneys and skin.

Solvent Safety

Recognize the Risks. The first step to ensuring safe use of solvents in your workplace or studio is to identify the hazards. Prior to working with any solvents, alert your employees of the dangers of these substances. Avail them of the appropriate safety data sheets (SDS) for these solvents, and provide them with any required safety equipment (safety glasses, gloves, air respirator) and appropriate training. Keep Safety Data Sheets (SDS) for any solvents that you use in a binder accessible to your employees. In an emergency, these bulletins can provide medical personnel with critical information.

Labeling Standards. Make sure that all containers for your solvents are labeled in accordance with the HazCom2012 standards. You should also instruct your employees on how to read the labels and recognize the terminology and pictograms used to alert users of chemical hazards.

Good Ventilation. Always work with solvents in a well ventilated area of your shop.

Personal Protective Equipment. Depending on the type of solvent used, you and your employees could be required to wear safety equipment, which could include protective eyewear (safety goggles or face shields), chemical resistant gloves and air respirators. If you are working in a confined space, where it is impossible to reduce a high concentration of solvent vapors, you should use an appropriate air respirator. When working with this equipment, follow these rules:

  •  Make sure that the respirator is tight fitting to get the full benefit of the equipment.
  • Provide employees necessary training.
  • After using the respirator, remove the cartridges and store in an air tight container.
  • Replace old cartridges.

Fire Safety. Store solvents in a flameproof cabinet. Have dry chemical fire extinguishers mounted in accessible places in the solvent storage area and throughout your shop. Dispose of solvent laden rags in an airtight metal fireproof container. Prohibit smoking in all work areas of your shop.

Disposal. Never dispose of solvents down the drain. Most likely this is an illegal activity. In most cases, you should let small amounts of waste solvents evaporate outside into the open air. Never dispose of rags soaked in solvent into the garbage. In some cases, rags can spontaneously ignite. If you have questions regarding disposal of waste materials, solvent-laden rags and procedures covering accidental spills, call your local governmental agency.

Product Evaluation

In evaluating which solvents to use and stock in your shop you should consider a variety of factors listed below. You can find much of this information in Safety Data Sheets for these products.

  • Application (the recommended uses for a particular solvent)
  • Evaporation Rate (the time it takes for a solvent to evaporate)
  • Flash Point (the temperature at which a solvent can ignite)
  • Flammability Rating (rating on a scale of 0 lowest to 4 highest)
  • Toxicity (the exposure limits for the solvent. Exposure limits are often provided by government agencies, such as OSHA, as a PEL or Permissible Exposure Limit value. The lower the number, the more toxic the solvent is. For example, turpentine has a PEL rating of 100ppm versus mineral spirits with a rating of 400ppm. Based on these values, you would deduce that mineral spirits is less toxic than turpentine.)

Some solvents, when used as a thinner or in paint mediums, can impart a yellowish hue to the painting. Prior to using a solvent, it is best to Test, Don’t Guess. To check the clarity of the solvent, brush a little of the solvent on a bright white piece of paper. After the solvent evaporates, inspect the appearance of the paper for any discoloration.

Many solvents can be used for the same application. Each solvent, however, has its own unique performance properties. The purpose of this story is to review the most common sign painting solvents explaining recommended applications, advantages and disadvantages, along with discussing procedures for safe handling.  

Pure Gum Turpentine

For many artists, old school sign painters and pinstripers, there is nothing like the smell of pure gum turpentine. It smells like a genuine sign shop or studio. I love the smell too. The problem is that the fumes are toxic.
By the time you can smell turpentine, it is already in your blood stream. For that reason, you should use turpentine in a well-ventilated shop and only use it when you absolutely need to. For cleaning your brushes, the slower evaporating mineral spirits (also called white spirits) is a much less toxic alternative.

Nevertheless, many believe that when turpentine is used safely, it is the best choice for thinning oil paint or lettering enamel. And for all practical purposes, it is your only choice when dissolving Damar resin or other resins.

Pure gum turpentine is made by distilling pine tree sap. There is not much difference between pure gum turpentine sold at your local hardware store and bottles of turpentine at the art store other than the price. In my opinion, the difference is about as significant as that between regular vegetables and organic vegetables. Both are made the same way. Both look alike. The quality is the same. And both perform identically.

In buying turpentine, inspect the clarity. It should be clear not yellow. When you buy turps, only buy in small quantities because it can yellow over time. 

Applications: Paint thinner (excellent choice for artist’s oil paints and lettering enamels); thinner for mediums; Damar resin solvent
Evaporation Rate: Fast
Flash Point: 95°F (35°C)
Flammability Rating: Flammable
Exposure Limits: OSHA PEL: TWA 100 ppm (560 mg/m3)

Mineral Spirits

For cleaning brushes and thinning paint and varnish, mineral spirits is good alternative to turpentine. It is also a cheaper alternative. While minerals spirits were originally developed as a dry cleaning solvent, painters discovered that it did a great job of cleaning brushes and thinning paints. Today, they are the most widely used solvents in the painting field.

Compared to turpentine, mineral spirits are also recognized as a much safer alternative. One reason is that mineral spirits evaporate much slower than turps, which means that there is much less of it in the air to breathe.

Mineral spirits is actually a mixture of several different solvents distilled from petroleum. The composition of that mixture can vary greatly from one manufacturer to another. That could be a problem, because you never really know what you are getting. For this reason, many of the old sign painters and artists use mineral spirits for cleaning brushes but not for thinning paint and certainly not for making a painting medium or Damar varnish.

Some painters prefer using mineral spirits as a paint thinner because it evaporates more slowly than turpentine. This gives the fine art painters a longer open time to manipulate the paint. However, if you are in a rush, as many sign painters are, a slower drying paint is not a benefit.

Applications: Paint thinner; brush cleaner, resin solvent
Evaporation Rate: Slow
Flash Point: 105°F (35°C)
Flammability Rating: Combustible
Exposure Limits: OSHA PEL: None

Denatured Ethyl Alcohol

Denatured alcohol is ethanol to which toxic chemicals are added, so people don’t drink it. The problem with denatured alcohol is that there is no telling what types of chemicals are used and in what amount to make the alcohol undrinkable. It varies from one manufacturer to another.

Generally, the chemicals don’t affect the properties of the alcohol. For prepping vehicle surfaces prior to vinyl application it is suitable. Isopropyl alcohol, however, is probably a better choice, if cleanliness is a concern.

Denatured alcohol is also used to dissolve shellac flakes. If you are a purist, you can buy a shellac solvent from Tools for Working Wood. It is denatured ethanol with the least amount of denaturant allowable in it. It’s great for dissolving the flakes, but it is expensive. In fact, it might be cheaper to use grain alcohol.

Applications: Surface cleaner; shellac solvent
Evaporation Rate: Fast
Flash Point: 60°F (16°C)
Flammability Rating: Highly Flammable
Exposure Limits: OSHA PEL: TWA 1000 ppm (1900 mg/m3)

Lacquer Thinner

Lacquer thinner is composed of many different solvents. It is a very volatile solvent. With respect to applications, I have listed it as a brush cleaner. I only use it to wash out brush oil from my lettering or pinstriping brushes immediately followed by rinsing the brush in mineral spirits. Many painters won’t go near the stuff. It can damage brushes. If used as a substrate cleaner, it can damage surfaces. The mixture of solvents in lacquer is also very hazardous to your health.

Applications: Paint thinner, adhesive remover, brush cleaner
Evaporation Rate: Very Fast
Flash Point: 60°F (16°C)
Flammability Rating: Extremely Flammable
Exposure Limits: OSHA PEL: None

VM&P Naphtha

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. The VM&P stands for “Varnish Manufacturing & Painters”.  VM&P Naphtha evaporates much faster than either turpentine or mineral spirits, which accelerates drying times.

Caveat emptor: there are different types of naphtha that 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.

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.
Applications: Paint thinner (great for spray painting); brush cleaner
Evaporation Rate: Fast
Flash Point: 55°F (13°C)
Flammability Rating: Highly Flammable
Exposure Limits: OSHA PEL: None


Toluene is used in many paint thinners, cleaners and adhesives. It is also used in some adhesive removers. Misused it is dangerous stuff. If you breathe enough of it, you will get as high as a kite. The danger is that it can damage your central nervous system, liver and kidneys.

If you are removing graphics, I suggest using a safer adhesive remover than one with toluene. If you must use this solvent, do not use it in a confined space. You need good ventilation and in some cases you should use an air respirator.

Breathing its fumes is not the only way that toluene can enter your system. You can also absorb it through your skin. For this reason, you should use nitrile gloves when working with adhesive removers or cleaners containing toluene.

Applications: Ingredient in adhesive removers
Evaporation Rate: Fast
Flash Point: 45°F (7°C)
Flammability Rating: Flammable
Exposure Limits: NIOSH REL: TWA 100 ppm (375 mg/m3). Toluene is the nasty solvent in airplane glue that makes you high if you sniff it. Based on personal experience, you can become intoxicated within 10 minutes of exposure from the fumes of adhesive removers containing toluene. When working with anything containing toluene, I would strongly recommend wearing an air respirator.

Wax & Grease Remover

For painting prep and surface prep prior to vinyl application, wax and grease removers are essential. The composition of solvent cleaners varies from one manufacturer to another. Typical ingredients include mineral spirits, naphtha, heptane and toluene. Some formulations are very aggressive, while others are mild.

Because ingredients vary greatly, always read the safety data sheet (SDS) prior to use. To ensure you don’t damage the paint system of a car or truck, test the solvent on an inconspicuous area of the vehicle before using it.

Wax and grease removers are comprised entirely of flammable solvents and typically have a flash point lower than that of turpentine. When working with these solvent cleaners always wear protective gloves, such as neoprene gloves, and wear safety glasses with side shield. Work in a well ventilated shop when prepping a surface for painting or vinyl application.

Xylene (Xylol)

When I was installing vehicle graphics, I frequently used xylene as a cleaner for oily dirt. Many decal installers do the same thing. Xylene is a very hazardous solvent and should only be used with care. Protective gloves are a must.

Applications: Surface prep
Evaporation Rate: Fast
Flash Point: 90°F (32°C)
Flammability Rating: Flammable
Exposure Limits: TWA 100 ppm (435 mg/m3)


Working with solvents is unavoidable in painting. Some applications, such as spray painting and substrate preparation, expose us to higher levels of solvent vapors. What’s more, accidents, such as solvent spills, can and do happen. Proper education and adherence to safety guidelines can help us minimize the hazards. Your employees must have training covering the solvents that they use and must have access to all pertinent information such as Safety Data Sheets (SDS). By understanding the properties of the solvents that you use, you can select the right solvent for the job as well as choose the less toxic and less volatile alternatives available.