Having the right tools and materials is crucial for achieving a smooth and professional finish when taking on a painting project. Two products commonly used are paint thinner and mineral spirits. At first glance they seem interchangeable, but there are distinct differences between the two solvents.
Paint thinner is a general term for liquid solvent thinning oil-based paints, cleaning brushes, and other equipment. Mineral spirits, on the other hand, refers to a specific type of paint thinner made from petroleum distillates. While both can be used for similar purposes, mineral spirits and paint thinners have varying properties that impact their suitability for different applications.
This comprehensive guide will clarify the confusion surrounding mineral spirits versus paint thinner. We’ll explore everything from their chemical composition and toxicity, to cost considerations and versatility of use. Understanding the nuances between these two solvents will ensure you choose the best product for the job.
The key difference between mineral spirits and paint thinner is their chemical structure.
What Are Mineral Spirits?
Mineral spirits are a petroleum-based solvent created through the distillation of crude oil. They consist mostly of aliphatic hydrocarbons and aromatic hydrocarbons like xylene and toluene. Manufacturers can produce a high-purity liquid with consistent evaporation rate and low odor suitable for paint thinning and cleaning by further distilling and purifying these petroleum spirits.
Stoddard solvent is the most common type of mineral spirits used today. It’s composed of hydrocarbon chains between C7 to C12, with a boiling point ranging from 145°F to 210°F (63°C to 99°C). Mineral spirits are classified as a Type 1 solvent with low volatility and toxicity. They have relatively low vapor pressure which reduces evaporation.
What’s in Paint Thinner?
Unlike the consistent formula of mineral spirits, the composition of paint thinners varies widely. Manufacturers blend different solvents to achieve the desired properties for thinning paint.
Some examples of chemicals commonly found in paint thinners:
- Turpentine – Distilled from pine resin, turpentine is probably the most common ingredient in paint thinner. It’s highly effective at cutting through oil-based paints. Turpentine has high volatility and a strong odor.
- Acetone – A powerful solvent known for its fast evaporation and ability to dissolve paint resins. However, it can cause paint to dry too quickly.
- Naphtha – A petroleum solvent similar to mineral spirits but more volatile. Different types include VM&P naphtha and petroleum ether.
- Toluene – An inexpensive paint thinner derived from petroleum or coal tar. Toluene is very strong and can damage paint finishes.
- Xylene – Another solvent frequently used in paint thinner for its versatility. It can be derived from petroleum or coal tar.
- Alcohols – Ethanol, methanol, and isopropanol are sometimes added as co-solvents to improve paint thinner performance.
- Ethers – Diethyl ether is a mild solvent found in some thinners.
Combining these chemicals gives paint thinner a high evaporation rate for quick drying and strong solvency power to cut through thick paint. However, the unpredictable formulation also makes paint thinner properties vary between brands.
Despite their compositional differences, mineral spirits and paint thinner serve similar purposes for oil-based paints and finishes. Their primary uses include:
Oil-based paints can be too viscous straight from the can for proper flow and leveling. Adding a small amount of solvent allows the paint to spread more smoothly onto surfaces. Mineral spirits are ideal for fine finishing work because of their mild odor and slow evaporation rate. Paint thinner can also be used, but care must be taken to avoid over-thinning the paint.
Paint thinner and mineral spirits both dissolve oil-based paint residues rapidly. They provide fast cleanup of paint brushes, rollers, and spray equipment. Mineral spirits are less irritating to skin, while paint thinner fumes require careful ventilation during cleaning.
Removing Grease and Grime
In addition to paint, mineral spirits can cut through grease, adhesives, rust, and other grime. This versatility makes them useful for general cleaning and degreasing needs beyond painting projects. Paint thinner is generally too harsh for non-paint cleaning uses.
Fueling Heat Sources
In some cases, paint thinner and mineral spirits may be used as fuel for torches, fondue pots, and antique oil lamps that require a petroleum-based liquid fuel. However, they must be cautiously burned due to potential toxicity from fumes.
DIY Wood Finishing
As a mild solvent, mineral spirits can be combined with beeswax and oil to create homemade wood polishes, finishes, and protectants. They slowly evaporate while enhancing wood grain beauty. Paint thinner is too strong for most wood finishing needs.
Both solvents may be used to clean car parts and thin paint and primer in auto body repair. Mineral spirits are preferred here for their lower odor, slower drying time, and decreased risk of harming paint finishes.
Evaporation Rate and Paint Quality
A key distinction between mineral spirits and paint thinner is evaporation rate. This greatly impacts the finish quality when solvents are mixed into oil-based paints and stains.
Mineral spirits have a relatively low evaporation rate. Their slow drying time allows paints to level properly onto surfaces before hardening. This provides an ultrasmooth final finish.
Paint thinner combinations like turpentine and acetone dry rapidly. While this speeds up project timelines, it can leave behind brush marks and uneven areas on finished paintwork. The quick-drying nature of paint thinner also makes oil-based paints prone to trapping bubbles as they cure.
The ideal solvent for thinning will balance quick-drying power for efficient application with slow evaporation for ensuring paint quality. This is why many painters keep both mineral spirits and paint thinner on hand. Mineral spirits provide superior finished results, while paint thinner accelerates drying between coats.
Toxicity and Safety
When selecting a paint solvent for your home or workshop, toxicity is a significant concern. Breathing in solvent fumes can cause dizziness, nausea, and other health effects. Some ingredients like toluene and xylene are known carcinogens with long-term exposure.
Mineral spirits have relatively low toxicity and vapor pressure. Proper ventilation is still recommended, but mineral spirits are considered one of the safest conventional paint thinners.
Paint thinner toxicity varies based on composition but is more hazardous than mineral spirits. Some types contain highly volatile chemicals and require great care to use safely. Reading product Safety Data Sheets is important to understand the specific risks associated with any paint thinner.
General safety tips when using either solvent:
- Work in a well-ventilated area away from sparks or flames.
- Use latex gloves and eye protection to minimize contact.
- Store in tightly sealed metal containers approved for flammable liquids.
- Never pour unused thinner back into the original container. This avoids contamination.
- Use only the minimum amount of solvent needed to reduce exposure.
Responsible handling and proper precautions allow paint thinner and mineral spirits to be used safely. However, less toxic water-based paint strippers and cleaners are also available for those wanting to limit solvent risks completely.
Another key factor when choosing between mineral spirits and paint thinner is cost. Mineral spirits are more expensive than most generic paint thinners per gallon.
Here is an approximate price comparison:
- Mineral spirits = $10 to $15 per gallon
- Paint thinner = $6 to $12 per gallon
- Odorless mineral spirits = $15 to $20 per gallon
Remember that prices vary based on brand, container size, and region. Bulk quantities offer the best value for those requiring large volumes of solvent.
Despite their higher upfront cost, mineral spirits may provide savings in the long run. Their versatility, reusability, and ability to be stored indefinitely make mineral spirits a sound investment for any painter’s tool kit. Lower-quality paint thinners dry out and become unusable over time.
Odorless mineral spirits are the most expensive option. However, the lack of harsh fumes can be worthwhile for those sensitive to chemical odors or allergies.
Versatility in Applications
While mineral spirits and paint thinner overlap for thinning oil-based paints and cleanups, mineral spirits provide additional versatility, making them useful beyond just painting projects.
Here are some of the diverse uses and advantages of mineral spirits compared to regular paint thinner:
- gentler cleaning – Mineral spirits won’t damage surfaces the way paint thinner can
- fine woodworking – Safe for finishing and conditioning all types of wood
- automotive uses – Won’t harm paint finishes or rubber bushings
- odorless options – Available with less smell for indoor
Can I substitute paint thinner for mineral spirits?
It’s not recommended to substitute paint thinner when a recipe or procedure specifically calls for mineral spirits. The unpredictable solvent blend in paint thinner could lead to poor results or damage. However, in some cases paint thinner can be used for general thinning and cleaning in place of mineral spirits if needed. Start using 25% less paint thinner than the recommended amount of mineral spirits to avoid over-thinning.
Are mineral spirits toxic?
Mineral spirits contain petroleum-based hydrocarbons that can be harmful with prolonged exposure. They are less toxic than many of the harsher chemicals in paint thinner but should still be handled with care. Using mineral spirits in well-ventilated areas and wearing protective gear minimizes health risks.
Can you mix paint thinner and mineral spirits?
There are no chemistry issues or dangerous reactions from combining paint thinner and mineral spirits. This can be done to modulate the evaporation rate. For example, equal parts mineral spirits and paint thinner create a moderately fast drying blend. However, blending will also dilute the milder properties of pure mineral spirits.
Is acetone the same as paint thinner?
Acetone is a strong solvent used as an active ingredient in some paint thinners. On its own, acetone dries extremely fast. In some situations, it can be used as a substitute for paint thinner, but acetone’s high volatility requires extra care. Paint thinner contains additional lubricating oils and slower evaporating solvents not found in pure acetone.
What is a good substitute for mineral spirits?
- Odorless mineral spirits have less smell but similar performance.
- Citrus-based solvents made from d-limonene can also substitute for mineral spirits.
- Alcohols like denatured alcohol work as paint thinners but are more toxic.
- Latex paint removers and cleaning gels are gentler water-based alternatives.
- Vegetable oil or turpentine can also thin and clean oil paints effectively.
Understanding the composition and properties of mineral spirits and paint thinner allows you to select the best solvent for a given task. Mineral spirits balance performance and safety, making them versatile for most oil-based painting jobs. Meanwhile, paint thinner provides stronger solvent power but requires cautious handling to avoid potential hazards.
While not exact substitutes, mineral spirits and paint thinner can be used interchangeably in many basic applications. However, mineral spirits offer advantages like smooth finished results, mild odor, low toxicity, and reuse potential, making them a superior all-around solvent for any painter’s toolkit. Knowing when to utilize the unique benefits of each solvent will result in successful painting experiences from start to finish.