Mineral spirits have long been a part of the painter’s tool kit, making it also a part of the woodworker’s tool kit. Yet many woodworkers know no more about mineral spirits than to know it can be used as paint thinner. Some don’t even know which paints it can be used with. There are many questions about this solvent, with woodworkers asking if they should use mineral spirits on wood before staining? As well as wondering if mineral spirits damage wood?
To start with, mineral spirits, which are also known as “white spirit,” “mineral turpentine,” and “turpentine substitute” is a petroleum derivative. The word “mineral” in the name makes reference to the substance being of mineral origin; in this particular case, from petroleum. Other thinners, such as turpentine are distilled from fermented grain and fruit.
Many people use the terms “mineral spirits” and “paint thinner” interchangeably; but they are not. While mineral spirits are a very effective paint thinner for oil-based paints and varnish, not all paint thinners are mineral spirits. Some may contain a small amount of mineral spirits in them or use other solvents to thin the paint, leaving mineral spirits out altogether. This has become a trend in recent years, as paint manufacturers have moved to water-based solvents, both for easier cleanup and lower environmental impact.
Being petroleum based, mineral spirits are a very effective solvent, not only for oil-based paints, but for anything which is oil-based, including non-petroleum oils. This makes it very effective for cleaning oily engine parts and other items which are encrusted in oil, grease and grime.
What is Mineral Spirits Used for?
Mineral spirits is a versatile product with a multitude of uses. It makes a handy degreaser; useful for cleaning tools, auto parts, and paintbrushes. It is also useful for removing sticky price tag residue, removing scuff marks off your floor and clean sap off of garden tools. You can even use it as a starter fluid for your charcoal grill. But it is most commonly known for its use as paint thinner, especially for use in cleaning paint brushes that have been used with oil-based paints.
As a paint thinner, mineral spirits offer compatibility with many oil-based paints and polyurethane varnish, although it is not compatible with lacquer or shellac. Lacquer requires its own solvent and shellac is alcohol based. You should always check the paint’s label to ensure that mineral spirits are the right choice before using it, and you should look into specific thinning ratios before using it to change the viscosity of paint, before using it, so as to ensure that your paint ends up the proper consistency.
You can also use mineral spirits to clean wood surfaces such as cabinets and floors. Because mineral spirits can soften certain finishes, it’s important to test an inconspicuous area before applying the spirits. Don’t use mineral spirits on no-wax floors, since it will remove the glossy top finish layer and create a dull, unattractive appearance. However, mineral spirits won’t damage any wood finish.
Last but not least, some woodworkers have found that cleaning wood with mineral spirits is the best way to prep new wood for a beautiful finish.
How to Use Mineral Spirits on Wood Restoration Projects
Mineral spirits are used more for working with wood, than for any other purpose. This inexpensive product is excellent for removing grime and buildup from a variety of finished surfaces. It cuts through old polish and wax, revealing the original finish beneath.
If wood cabinetry, doors, trim or furniture looks dull or murky, it is probably nothing more than a buildup of dirt and grime on the finish. Mineral spirits can be used to clean off this grime, restoring the original luster of your wood’s finish.
If you’re using mineral spirits to clean wood that has already been stained or finished, it is best to work with a soft cloth, pouring the mineral spirits onto it and scrubbing the surface with the cloth. Add additional mineral spirits as needed and change to a new area of the cloth when it gets dirty. In some cases where buildup has been accumulating for years, you may need to use a pad of extra-fine steel wool or a light ScotchBrite pad to cut through the grime. A smaller brush such as an old toothbrush will help you reach into any cracks or crevices.
Be patient when using mineral spirits to clean, since it can take a little while for the spirits to penetrate into and tough, grimy layers. Once you’re finished, you’ll be rewarded with a look at the original clear finish. Many people find that this is a great alternative to stripping and refinishing.
How to Clean Wood before Staining
Mineral spirits can also be used for cleaning wood projects, before applying any finish. This provides an excellent way of cleaning the wood’s surface. It also promotes the absorption of stain into the wood, giving you a richer finish.
As with most woodworkers, you’re probably accustomed to sanding all your projects, before staining. But as any experienced woodworker can tell you, working with the sander is just the first part of getting a fine finish. Once you’ve achieved a smooth, even surface, it’s important to clear away all the sawdust and sanding particles, before applying any finish, so that your finish will look the way you want it to.
The question then becomes how to clean the wood after sanding? If you don’t clean it the sawdust ends up in your finish, making bumps where you wanted something glassy smooth. The best way to get a clean surface, which is ready for staining or varnishing, is to use mineral spirits after sanding is complete.
Start by pouring a small amount of mineral spirits onto a clean, lint-free shop rag. Gently wipe all surfaces of the wood with the rag, moving slowly and using even strokes, staying with the grain of the wood. Do not use circular or scrubbing motions.
When cleaning wood with mineral spirits before staining, keep switching to a clean portion of the shop rag as you pick up debris from the wood’s surface. If you’re working on a large project, you may find that you need to use more than one rag to get the job done right.
Make multiple passes over the wood to ensure that you’ve removed all the sawdust. After using mineral spirits to clean wood, it’s important to take a moment to rub the wood with a dry cloth, removing any remaining mineral spirits from the wood’s surface. Obtain a fresh, clean, lint-free shop rag and wipe the wood’s surface, again staying with the grain. Make several passes with the rag to ensure that you’ve removed all the mineral spirits possible.
It is necessary to allow the mineral spirits to dry, before applying finishes. This usually takes from 15 to 20 minutes. You’ll be able to tell when the wood is dry, because it will no longer look wet, but will have returned to looking dry, as it did before you started. This is usually most obvious because of a change in the wood’s color.
Don’t Stop There
In the process of applying a fine finish to woodwork, it is always a good idea to sand lightly between coats, using fine sandpaper and light pressure. This works to remove and bumps made by dust particles in the finish and is a fine opportunity to check the project for imperfections in the wood that might need wood filler applied. Many woodworkers wait until after the application of the first coat of varnish, before applying wood filler, so that it doesn’t discolor the wood around the hole.
Once again, this is a great opportunity to use mineral spirits to clean the project between coats of polyurethane and other compatible finishes. You don’t need to concern yourself so much with the direction you wipe it in this time, except on open-grain woods that aren’t filled. Wiping across the grain in that case, could cause the sanding dust to go into the grain, where it will end up in the next coat of finish. Always be sure to wipe off any excess mineral spirits before moving on to the next coat.
Using Mineral Spirits as a Cleaner
As mentioned earlier, mineral spirits can also be used as a cleaner for greasy parts, such as automotive parts, or for cleaning sap off of tools and sticky labels off of just about anything that has a non-porous surface. Since it is a distillate of petroleum, it is an extremely good solvent for anything oil-based that needs to be cleaned off, whether that is a petroleum based oil or a plant based oil.
When used as a cleaner, mineral spirits can be used like any other liquid cleaner, applied to the object to be cleaned with a rag or pouring it on the object. You can even soak automotive parts in mineral spirits, using it as a degreaser.
It is helpful to use a rough cloth or a stiff brush when cleaning grimy, oil-encrusted parts. While the mineral spirit makes a great solvent, it can take a while for that solvent to soak into the grime you are trying to remove. Using a stiff brush helps by removing what is already softened, so that the mineral spirits can get to the grime below.
Once all the grime has been removed from the part, wipe off any excess mineral spirits. The part can then be painted, if necessary. Don’t worry if you can’t get the part 100% clear of any mineral spirits residue, which can be hard to remove on rough cast parts, as spray paints are oil based and will mix fine with the mineral spirits.
Mineral Spirits Safety Tips
Because mineral spirits are classified as an irritant to skin, it’s important to wear gloves when applying it to wood and other surfaces. If there is a risk of splashing, you’ll want to wear safety glasses or goggles to protect your eyes.
Always wash your hands and other exposed skin after using mineral spirits. Because it is oil-based, mineral spirits leave your hands feeling oily. Washing with soap and water will remove this residue. Prolonged contact can lead to chemical burns. Mineral spirits will also dry your skin, causing the skin of your hands to crack. It’s a good idea to use hand lotion to moisturize your skin, if you are using mineral spirits frequently.
Be sure to use mineral spirits in a well-ventilated area, or wear a respirator if you’re not able to provide adequate ventilation. Close contact with the vapors can cause serious side effects including dizziness and nausea. With continued exposure, there is a chance of unconsciousness.
Do not smoke while using mineral spirits; it is flammable.
Store leftover mineral spirits in a tightly sealed container, away from areas where heaters and/or open flames are present. If you have more than 25 gallons of flammable material stored in your shop, you need to have an approved flammable storage cabinet per OSHA regulations. While you can get away with not having one in a home workshop, as nobody will be inspecting it, it’s still a good idea to use a flammable material cabinet, for safety reasons.
After using mineral spirits on wood and other surfaces, be sure to dispose of the solvent properly. Do not pour it on the ground or down the drain. Instead, place used mineral spirits in a sealed container and take it to a hazardous waste collection point in your community.
If you can’t find where your community doesn’t have a public hazardous waste collection point, check with your local paint store. They may offer that service, or know where you can take your waste materials.
Do not throw shop rags into the trash after using mineral spirits to clean wood or other surfaces; mineral spirits are volatile and can cause a trash fire. Obtain a jar, coffee can, or other container with a lid that can be sealed shut. Place the rags inside and submerge them in water. Seal the container and take it to a hazardous waste disposal center or keep it safely stored until your community trash pickup service offers a hazardous waste pickup day.