Should Mineral Spirits Be Milky? DIY Advice!

Like many DIYers, you turn to good old-fashioned mineral spirits as a paint thinner, metal parts cleaner, or finish wood between sanding and staining.

Suddenly, your once clear container of solvent looks milky. You’re not alone—DIYers like you, whether painters or auto mechanics, would be concerned over this new development. 

So, should spirits be milky? 

No, mineral spirits are only cloudy or milky when impure. Pure white spirit is a petroleum distillate and is clear or transparent. Some green energy-conscious brands sell products containing 20 to 40 percent mineral spirits.

This article will explore the reasons why spirits turn milky—and what to do about it.

Why Do Mineral Spirits Turn White?

There is only one reason your mineral spirits have a milky or cloudy color: It is impure and contains water or slow-evaporating alcohol. 

Pure spirits are becoming scarce in most hardware stores due to the push for more “green” and environmental-friendly products. 

Furthermore, brands are shifting to milky mineral spirits due to the difficulty and safety hazards of handling spirits. Therefore, these brands may add water or other less-reactive solvents that are easy to use and biodegradable in the environment. 

What’s more? Some “green” spirits also contain acetone or alcohol.

How Do I Spot “Green” or Milky-Colored Mineral Spirits

Thankfully, you don’t need to break the seal before knowing what you’re getting. On your next visit to the hardware store, hold the solvent container and turn it to see the composition details written on the back. 

Note that the details might differ, but you will get something along these lines. Impure or “green” mineral spirits will also contain the following details:

  • Specific gravity: 33% ±2%
  • Flashpoint: greater than 200°F.
  • Solubility: 65 percent.
  • Composition: 30-40% hydro-treated light distillate (petroleum) CAS 64742-47-8. 

According to the MSDS database, milky-colored mineral spirits contain a 1:2 mix of solvent to water. Furthermore, milky-colored, impure spirits will have an estimated specific gravity of 33% ±2%. The flashpoint will also fall within >200°F. Pure spirits have a flashpoint within 100°F. Likewise, impure spirits in the ratio of 1:2 will have a 65 percent solubility in water.

Note: Flashpoint is the temperature at which an organic compound releases enough vapor to combust in the air. 

Are Milky Mineral Spirits Safe to Use?

Yes, milk-colored mineral spirits are safe to use. It is why brands are producing more of these “green” solvents

On Lowe’s website, a product review revealed that impure spirits have zero combustibility factor. 

In other words, it does not ignite or cause fires irrespective of the temperature. Furthermore, it does not give off fumes, unlike 100% pure mineral spirits. Milk-colored or impure spirits also evaporate slower than clear spirits. 

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Can I Use Milky-Colored Mineral Spirits in DIY Home Projects?

Milky-colored spirits have impressive qualities. However, these qualities have robbed it of a lot of functions. It’s no surprise that many DIYers have raised numerous complaints about its incompatibility in some DIY applications.

You can’t use mineral spirits for thinning oil-based paints. “Green” spirits contain water molecules, which react and do not mix well with oil-based stains. You will notice the separation between oil-based paints and “green” spirits.

Are you thinking of using “green” spirits to thin polyurethane or shellac? Think again—it does not mix well with poly or shellac, either. Most reviews contain reports of “green” spirits not mixing with polyurethane or shellac. 

Also, it is not suitable for thinning epoxies or lacquer.

However, these excellent solvents are not so bad for cleaning sanded wood or removing paint from paint brushes. Furthermore, it is easier to handle since you don’t need to take extra safety precautions. 

Soak the paintbrush into the paint solvent and wait till the paint softens enough. Also, apply it on a lint-free cloth to remove dust particles and stains after sanding.

Note: Green mineral spirit may have lesser cleaning power than clear spirits. So, you may need to apply more pressure when scrubbing hard-to-remove stains. 

Also, it evaporates slower than clear spirits. Wait for at least one hour before adding a new finish after using “green” solvents.”

Do Milky Mineral Spirits Go Bad?

DIYers are often concerned about the shelf life when asking, “Why are my mineral spirits milky.” 

Milky or cloudy-colored mineral spirits may have a shorter shelf-life than pure white spirits. Water molecules present in spirits may encourage the growth of microorganisms that will later degrade the solvent. 

This is why kerosene has a short shelf-life: microorganisms grow in kerosene and spoil it over time. 

Pure spirits can last for decades without decreasing efficiency. As a pure petroleum distillate, it contains no water molecule to encourage the growth of microorganisms. 

How to Use Milky Mineral Spirits

You can use “green” mineral spirits to clean sanded wood or remove stains. Follow these instructions to use it after sanding or for stain removals.

How to Use “Green” Mineral Spirit” After Sanding

  1. Soak a rag in the solvent
  2. Apply it to the wood surface;
  3. Scrub in the direction of the wood grain;
  4. Wait for the solvent to dry off before applying finish.

How to Use “Green” Mineral Spirit For Brush Cleanup

  1. Pour the necessary amount of solvent into disposable Tupperware.
  2. Dip the paint brush into the solvent, and ensure it is submerged completely.
  3. Watch if there’s a color change in the solvent.
  4. Remove and clean the bristles with a comb.

Conclusion: Should Mineral Spirits Be Milky?

Once again, pure mineral spirits must not have a milky or cloudy color. Cloudy spirits are impure and may contain plain water or slow-evaporating alcohol. 

So, bring up this article when your circle discusses whether those solvents should be a cloudy color or not. You might help someone figure it out as you did.