How to Thin Out Rust-Oleum for Spray Painting

The famous rust-protective paint brand, Rust-Oleum, comes ready-to-use in convenient spray cans. This is great if you are spray painting a surface that is small to medium in size, but what if you are needing to paint something larger, like a car or tractor? Rust-Oleum can also be bought in a paint can, but this type of paint needs some adjustment before you load it into your spray gun.

Rust-Oleum can be thinned by mixing it in a container with acetone, xylene, or mineral spirits. The correct ratio is 1 gallon of paint to 6.5 ounces of acetone. To get the right paint consistency for your spray gun, use a viscometer or simply test the paint and add more paint or acetone as needed.

What to add to Rust-Oleum to thin it.

What is Rust-Oleum?

Rust-Oleum is an oil-based enamel paint, which is why it is so effective at rust-proofing metal surfaces. It can be used on everything from metal roofing sheets to cars, farm or gardening tools, tractors, and even ships because it dries and cures to a hard, durable, glossy finish.

The Rust-Oleum paint that one can buy in ready-to-spray cans is perfect for small or medium surfaces, but it can get very expensive if you need to cover a large surface area. Luckily, one can also buy Rust-Oleum in paint cans. It is perfectly alright to apply Rust-Oleum using a paintbrush but to make the job go faster, one can use a spray gun.

Benefits of Thinning Paint When Using A Spray Gun

Applying paint using a spray gun will achieve a smooth, professional finish and cut down the time you spend painting hugely. It does, however, require the extra step of thinning the paint prior to loading it into the spray gun. Do not be daunted by the idea of mixing paint! It is easy to do, and there are many benefits to thinning paint when using a spray gun:

  • It increases the paint viscosity, allowing it to atomize and flow more easily from the spray gun’s nozzle.
  • Keeps your spray gun in good condition because paint does not block up the mechanism and make a mess.
  • Allows you to apply paint in thinner, more consistent coats to achieve a smoother, more durable finish.
  • It decreases the time it takes for paint to dry.

Is Thinning Rust-Oleum for Spraying Always Necessary?

There are certain scenarios where thinning paint prior to loading it into a sprayer is not necessary. For example, if you are using an airless spray gun that does not use a compressor.

Airless sprayers produce a much higher pressure than an HVLP (high volume low pressure) sprayer; therefore, they have more power to pump the paint into the mechanism. When using an airless sprayer, you do not have to thin the paint prior to spraying it.

What to Add to Rust-Oleum to Thin It

When using an HVLP sprayer that relies on a compressor, you need to thin Rust-Oleum to prevent it from clogging the tiny orifice of the nozzle. Rust-Oleum can be thinned with the following chemicals:

  • Acetone is the recommended thinning solvent for many Rust-Oleum paints. It causes paint to dry very quickly, especially on hot days. One should thin the paint between 10-15% and avoid over-thinning, as it speeds up the drying time too much.
  • Xylene. Rust-Oleum recommends using this solvent for their paints that have a hammered metal finish. Thinning up to 15% is the guideline. Xylene causes the paint to dry a little slower than with acetone, so it is better for painting large surfaces.
  • Mineral spirits should be used to thin certain Rust-Oleum products. It increases the paints drying time, and thus over-thinning (more than 20%) should be strictly avoided, as it may keep the paint from drying.

Always study the label of a specific Rust-Oleum product closely, as certain solvents are recommended for different products.

What is the Correct Ratio for the Perfect Paint Consistency?

Thinning paint to the correct consistency requires some trial and error, which is why it is important to have a scrap piece of material at hand that you can test the spray on.  Factors like temperature and humidity affect how much you need to thin paint.

Read the instructions for your specific spray gun to find the viscosity you need to thin to and read the recommended thinning guidelines on the paint. This should provide one with a good starting point.

Start by adding a small amount of solvent, an ounce at a time, if you are working with a gallon of paint. At around 6 ounces, you should reach the desired viscosity. Do not exceed 12 ounces of solvent per gallon of paint to avoid overthinning the paint.

How to Thin Oil-Based Paint for Spraying

It is best to gather everything you will need before you start the process of thinning the paint:

  • Wooden dowel or stick to stir the paint
  • A clean bucket large enough to stir the paint in
  • Thinning agent – acetone, xylene, or mineral spirits
  • Rust-Oleum paint
  • Paint spray gun and nozzles
  • Graduated measuring cup
  • Paint funnel
  • Viscometer (optional)
  • Face mask
  • Protective eyewear
  • Clean rag for wiping the nozzle
  • A piece of material similar to what you are painting to test on

Follow these easy steps to thin Rust-Oleum for use in a paint spray gun:

  1. Stir the paint thoroughly. This is an important first step because paint pigments settle at the bottom of the can. Rust-Oleum recommends that you begin by pouring off any separated liquid into a clean container. Stir the remaining paint in the can to break up any clumps and incorporate the paste from the walls and the bottom on the can. When the paint is smooth, gradually add the liquid that you poured off initially and stir to incorporate it. Pour the paint back and forth between two containers a handful of times to ensure it has a totally uniform consistency.
  2. Decant the amount of paint you need into a clean bucket. Only thin the amount of paint that you will be using for a project. Ensure that the bucket is big enough that you can stir the paint inside it.
  3. Prepare the test material. Have a piece of scrap metal, wood, or drywall ready so that you can test the spray paint consistency on it.
  4. Measure out an ounce of thinning agent and add it to the paint, stirring to incorporate it. Keep adding an ounce at a time until you have added about 6 ounces per gallon of paint, or the paint has reached the desired consistency. You can use a viscometer to check the viscosity if you have one.
  5. Add the thinned paint to the sprayer gun and do a test. Use a funnel to load the sprayer without making a mess. Spray an area of the test material to check the consistency. Is it flowing from the sprayer without any problems, then add all the paint to the sprayer and start painting.
  6. Adjust if necessary. If the paint flowing out in splotches, or you are getting uneven coverage, add a little more solvent to thin the paint further. If the paint has been thinned too much, it may run, in which case you should add more paint.
  7. Write down the correct ratio. This is helpful for future reference if you want to duplicate the consistency of the paint.
  8. Paint the surface, allowing the paint to dry completely between coats. Thinning the paint will reduce the time it takes for coats to dry.


Rust-Oleum oil-based paints can easily be thinned using acetone, xylene, or mineral spirits, depending on the product. Thinning the paint is necessary if you are using it in a spray gun because the viscosity of Rust-Oleum is too low for the paint to flow optimally from the nozzle. You may not have to thin paint if you are using a powerful airless spraying system.

Always read the instructions of the Rust-Oleum paint that you buy and consult the user manual for the spray gun to find the viscosity that is necessary. To thin Rust-Oleum, start by adding 6 ounces of thinning solvent to 1 gallon of paint, one ounce at a time. Test the paint on a scrap piece of material and adjust the consistency by adding more paint or thinning solvent as needed.

Thoroughly mixing the paint before adding any thinners is vital, as Rust-Oleum separates in the paint can.

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