How to Thin Wood Stain

how to thin wood stain

Staining wood has both aesthetic and finishing benefits for your woodworking project. For starters, staining helps preserve the wood so that it lasts longer. And, stain allows you to add color, texture, and even grain, improving the look and feel of the wood finish.

​However, some wood stains are thick and difficult to apply. Others are available in limited color varieties and may not match the color you have in mind for your project. If you learn how to thin wood stain, ​you'll be able to quickly and easily control the finished project you are looking for in your woodworking.

how to thin wood stain

​Benefits of Learning How to Thin Wood Stain

​While there are a lot of benefits to learning how to thin wood stain, here are the three largest benefits: 

​Easier To Apply

​When the stain is too thick, no matter if you brush it, back-roll it, or spray it onto the wooden surface, the results rarely live up to your expectations. You get traces, uneven textures, and you need to clean the brushes and unclog the sprayer all the time.

Thinning ​your stain helps out this problem quite a bit. You can move at a much slower pace because the stain goes on a lot slower. Granted, it will take you longer to achieve the same depth and darkness of color, but it will be easier to apply. 

Thinning out your wood stain also keeps it from drying out too quickly.

​Color Perfection

Getting quality stain in your favorite color tone is often an impossible dream. Even when you think you have found the perfect nuance, you might wish you could lighten it up a bit. You can, by thinning the stain and testing it until you’ve obtained the tone you were after.

This sort of color control doesn't come immediately. A tip: try buying the sample sizes at your local home improvement store, and practice mixing and thinning on these. Once you get the hang of it, you'll have a lot of options for controlling your stain color.

​More Bang for Your Buck

Thinning basically means adding more liquid to the stain, therefore obtaining a higher quantity. The resulting stain will also be thinner, so it will spread easier, and the same amount will let you cover a larger surface. 

In order to enjoy these benefits, you have to identify the right thinner for the paint you plan on using, and to use it in the right quantity. Adding too much thinner could make the stain less effective and even useless, or lighten it too much.

We will talk more about this in the following lines when reviewing the steps you need to take in order to thin wood stain and obtain the desired consistency and color.

Related: How to Apply Polycrylic

Which Stains Work Best for Staining

There are a variety of stains available today, and different types of stain are better for thinning:

  • ​​Water Based Stains: these stains have already been thinned with water or a commercial retarder, and generally don't really need to be thinned much (if at all). Water based stains don't contain the toxic VOC's that polyurethane finishes do, and so there is not benefit to your health in thinning it. The only reason to thin a water based stainer is to slow the application time down.
  • Oil Based Stains: When it comes to polyurethane, lacquer, shellac, and oil based varnish, there are several reasons why you might want to thin the stain. For starters, this type of stain contains very, very toxic VOC's that can be very dangerous... thinning the stain reduces the concentration of these VOC's. These stains are also highly flammable, so you'll cut down on that risk. Lastly, you'll get the benefits we described above.

How to Thin Wood Stain in 3 Easy Steps

Step 1 - Identify the Type of Stain and the Appropriate Thinner 

There are several types of stain on the market. Their composition determines the thinner you can use. In order to identify the right thinner for your chosen stain, the safest solution is to carefully read the label looking for manufacturer’s recommendations and ingredients.

Here is a list of the most common types of stain and the thinners that should work for them:

type of stain and thinner
  • Oil-based pigment stains – These stains contain mineral spirits, usually mentioned on the label as petroleum distillates, so the best thinner for them is mineral spirits.
  • Varnish stains – Although they are thicker than most oil-based stains, they too contain mineral spirits and can be thinned with it.
  • Water-based stains – Mostly recommended for exterior use, you can recognize them by their semi-transparent color and the word latex mentioned on their label. Water is the best thinner for them.
  • Lacquer-based (non-grain-raising) stains – They have a strong smell coming from the xylene, methyl ethyl ketone, or toluene in their composition. You should use a lacquer thinner for them.

Step 2 - Add the Thinner

To make sure you get the desired results, it is important that you add the thinner just before staining the wood. If you dilute the stain in advance and store it, especially if the lid is not well closed, it may turn into a pasty mass by the time you decide to apply it. ​

Except for varnish, all the other stains can be thinned and made workable again. It is best to thin them right before applying them to the desired wooden surface.

When adding the thinner, it is important to add small quantities and stir thoroughly to dissolve all the dye or pigment. If you add too much thinner, the stain could become too liquid and the color too light, case in which you may have to apply two or more layers in order to obtain the desired results.  

When using a spray gun, too much thinner can lead to running and dripping, so adding small quantities of thinner gradually is the best approach.

Related: Polycrylic vs Polyurethane - ​Upsides and Downsides of Each​

Step 3 - Test the Stain

Once you have added a small amount of thinner and mixed the stain thoroughly to obtain even color and texture, it is important to test the stain on a wooden surface similar to the one you want to use it on. If you don’t have such a surface available, you can test it on a small area that will remain out of sight.

The test will help you assess if the stain has the desired color and texture, or more thinner is necessary. You can repeat the procedure of adding a little more thinner, mixing the stain thoroughly, and testing it as many times as you need to until you obtain the results you desire.

Once the stain is thinned to the desired consistency and color, you can apply it on the wooden surface. Depending on what type of stain and thinner you use, what staining method you prefer, and where the staining takes place, consider following the tips below.


​Related: ​Learn the Process for Laminating Wood

The Best Products to Thin Wood Stain

As mentioned above, there are several different types of products you can use to thin wood stain. Here is an overview of each:

  • Mineral spirits (paint thinner): ​only to be used for thinning ​​​polyurethane and oil based varnish. While a lot weaker and less toxic than these stains, you still need to be careful with mineral spirits - don't breathe in for too long. When thinning, use roughly 4 parts stain to 1 part mineral spirits. This is flexible, as it really only effects how thick your stain ends up being.
  • Mineral spirit variations: ​there are several variations of traditional mineral spirits that are available to you. Turpentine is the old fashioned variant - it is now more expensive but does have a slow dry time. Varsol is a variation, and Naptha is a good equivalent (although more flammable with a shorter dry time). ​​​
  • ​Water: ​the best thinner for water based stains... seems obvious, right?

Tips on How to Thin Stain and Stain Wood Safely

  • Wear protective equipment. Some wood stains contain harmful chemicals, toxic to the skin and/or lungs. When thinning and applying them, you should wear protective equipment, like gloves, safety glasses, and even a top notch respiratory mask. Depending on the type of stain and thinner you use, failing to do so could result in skin irritations, headaches, nausea, dizziness, throat, nose and lungs irritations.
  • Ensure proper ventilation when thinning and applying the stain indoors. You can do so by opening doors and/or windows, or installing a fan. It will help you diminish the toxicity risks explained above and speed-up the stain drying process.
  • Avoid using thinners and stain near fire or heat sources. Some stains and solvents are extremely flammable, and their vapors may linger in the air for quite some time. One spark could be enough to start a fire and could jeopardize your life and your property.
  • When you are done thinning and applying the stain, clean your tools and equipment. If the stain is not dry yet, the same substance you used as a thinner should be able to clean it. If it is already dried or you are not satisfied with the results, you can try more powerful solvents, like acetone.

​Final Thoughts about Thinning Wood Stain 

As you can see, anyone can learn how to thin wood stain and obtain even, great looking surfaces. The trick is to use the right thinner, apply it in small quantities, mix thoroughly, and test the thinned stain until you obtain satisfactory results, all while staying safe.

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