Glad you are finding value in the wood finishing troubleshooting cheat sheet I’ve been sharing.
Big thanks to Blair L., Dan L., Barry, and Russ for their blog comments last week about, “Step 2: Stain and Topcoat Compatibility,” including…
“Keep the advice coming.”
“This is timely.”
“Seriously helped me.”
I must admit, it feels great knowing I’m helping you with your projects and getting your finishes to come out the way you want.
So, today, let’s talk about Step 3: Use and Compatibility of Primers and Pigmented Topcoats.
I take a lot of calls from finishers who are confused about what type of primer to use underneath their pigmented topcoats, and the concern is understandable. Nobody wants to ruin a project by using incompatible products.
Here are four of the most frequent questions I field about primer and pigmented topcoat compatibility:
Question 1: What should I use to control tannin or sap stain from bleeding through when finishing with a water-based paint or pigmented lacquer?
Answer: Using a stain-blocking primer is critical to block tannin and sap stains from bleeding up through the pigmented finish.
I’m sure you have seen red oak create a brownish-red blush that works its way up to the surface of the freshly applied pigmented finish. White oak, pine, ash (and sometimes certain cuts of maple) are also prone to this.
The staining effect is caused by acids in the wood fiber reacting with the higher pH of the water-based coatings, and by the sap (pitch) reactivating when exposed to moisture.
It is important to use a low pH acrylic, or a shellac-based primer to help neutralize and block the tannin or sap from bleeding through.
See below for a few popular brands I confirmed work well with our Emtech EM6500 Pigmented Lacquer Series.
One thin, reduced coat of a pigmented primer rated for stain-blocking is OK to use in this situation.
The primer you use can be alcohol or water-based, but it is important to remember to thin the primer with its assigned thinner by upwards of 50% so “checking” or “mud-cracking” doesn’t happen when the pigmented lacquer is applied over it.
Question 2: How should I prime a prefinished surface (such as old kitchen cabinet doors) when I don’t know what type of finish was originally applied to them?
Answer: With any unknown, you first must ensure the surface is clean and free of contamination (see my previous cheat sheet notes about surface preparation).
Once clean, you should use one of the types of stain-blocking primers listed below to ensure adhesion to the unknown finish is complete.
Some of the most reliable brands and types of primers are:
- BIN® from Zinsser (their alcohol-based version is preferred)
- Block-Out® or STIX® from Insl-X (which is a water-based acrylic)
- Benjamin Moore Fresh Start® (available in alkyd and water-based formats)
These are reliable primers that will bond to a wide array of substrates and will also control the dreaded tannin/sap stain we discussed above.
Just ensure you follow the directions for the specific brand of primer you use.
Again, keep in mind, some primers need to be thinned to prevent mud-cracking and crazing when surfacers (see below) and pigmented lacquers are applied over them.
Question 3: What do I use if I want to fill in the grain pattern to give the painted surface a flush, grain-free image?
Answer: This is where a special type of primer, called a surfacer, comes into play.
Surfacers are “ultra-high solids” versions of primers that help to fill and hide the negative grain on wood species such as birch, poplar and engineered surfaces such as MDF.
A good example is our Emtech HSF5000 Primer/Surfacer. HSF5000 will help prevent or completely stop the negative wood grain image from telegraphing, or “printing” back up through the pigmented topcoat.
Surfacers are used as the “Step-Two” in multi-step finishing processes to turn certain types of wood species into non-telegraphic substrates.
It is critical that you apply any surfacer coats in a thin wet film set – too heavy of a coat and you will be inviting mud-cracking somewhere down the finishing line.
Question 4: Can I use different types and brands of surfacers, primers and pigmented lacquers in my finishing schedule?
Answer: Yes, I have found the vast majority of water-based and solvent-based primers, surfacers and pigmented finishes will work just fine together as long as you follow the specific application procedures and dry-times of each part of the finishing equation.
Finally – and I will always repeat myself at this point – make sample panels and storyboards to confirm your finishing process and document your procedures before you take your final steps into the finishing room. Truer words…
I hope the above tips on getting primers and pigmented topcoats to “play nice” helps you achieve finish you’re looking for.
Stay tuned and watch your inbox for how to troubleshoot “Step 4: Drying and Curing.”
In the meantime, do you have any experiences, advice or questions about primers and pigmented topcoats compatibility? Please share your thoughts or read what others are saying in the comments section below.