What is a “Scratch Test”, and why is it so important?

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If you have seen the term Scratch Test, you are probably researching how to strip or restore your wood deck, fence or siding.  Before applying deck stain it is important to properly prep the wood.  It is possible to restore virtually any deck, fence or siding back to a fresh cut appearance.  The current condition of your wood will determine which process you follow.  The condition of the wood will also determine which deck stripper you use.  No matter what process you follow, you will likely need to perform a scratch test.

Woodrich Brand manufactures two different types of strippers to help you restore you wood deck, fence or siding.  The most important step when using either stripper is to perform a scratch test.  EFC-38 is specially formulated to help you remove dirt, grime, mold, mildew and the layers of dead grey wood fibers that form on unprotected wood.  EFC-38 will also strip most true oil based wood stains and sealers.  HD-80 was developed to help you strip flaking, peeling semi solid and solid deck stains and sealers.

How do strippers work?

Both products essentially help you in the same way.  The purpose of a deck stripper is to soften the existing stain or sealer, usually to a pudding like consistency.  The stripper will also soften any dead grey wood fibers.  Once everything on the surface of the wood is softened, you can easily remove it with a gentle power washing.  The goal is to let the stripper do its job, so the power washing is as effortless as possible.  This is where the scratch test comes into play.

How long it takes for either stripper to work depends on a lot of different factors.  The age of the wood, the age of any existing finish, the amount of build up on the surface, how deeply ingrained the dirt and grime all make a difference.  The amount of sunlight the wood receives is a big factor.  The temperature will even have an effect.  So the best way to know when it is time to power wash is to perform a scratch test.  Actually several scratch tests would be ideal.

Performing the Scratch Test

To perform a scratch test, you simply take a wooden object and gently rub or “scratch” the surface of the wood.  As a contractor, I most often used a stick from the yard.  When you purchase a wood deck stripper from Woodrich Brand, you will be provided with a scratch stick.  In this case it is a Popsicle stick with the Woodrich Project Support phone number etched into it.

Woodrich Brand Scratch Test Stick
It is important to perform a scratch test.

In most cases you can make your first scratch test about 15 min after applying the deck stripper.  Its important to keep the stripper wet the entire time.  If it begins to dry, mist it with more solution to keep it active.  It is best to perform your scratch test in an area that has been most protected from the elements.  For a deck, below the handrail and near the house are good areas to test.  With wood siding or log homes, high on the wall, just below the eves it a good area.  On a fence, look for an area that receives the least amount of sunlight or anywhere that look like it will be the most challenging to strip.

Remember you want to scratch with gentle pressure.  Your goal is to let the deck stripper do all the work.  You certainly wouldn’t want to scratch the surface any harder that you would scratch a puppy!  Keep performing scratch tests until you can easily expose fresh bare wood.  When removing multiple layers of solid stain it may take 30 min or more for the deck stripper to completely soften the finish.

When you can expose clean, bare wood anywhere you perform a scratch test, it is time to move on to the power washing step.


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