Painting Wood Furniture: How to Permanently Cover Knots and Stain
Painting wood furniture has its difficulties! Learn to permanently block tannin bleed-through from wood stains and knot holes with these two tried-and-tested options.
Also helpful: How to Choose the Best Paint for furniture – How to Refinish Wood Furniture (no sanding!) – Must Know Tips to Prep and Refinish Furniture
Painting Wood Furniture: Preventing Tannin Bleed-Through
(How to Permanently Cover Knots and Old Stain)
by Elisha of Pneumatic Addict
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I love to build DIY furniture. Sometimes it’s new, raw wood and sometimes I’m covering up an old finish.
Either way, I’ve had painted wood furniture projects that looked great to begin with then, especially with white or light paints, the tannins started to bleed through. Frustrating!
So just what are tannins?
Tannins are naturally-occurring compounds found in wood and other plants, including those in coffee, tea and grapes/wine. They help prevent disease and regulate the plant’s growth.
Because of their chemical nature, the tannins seep to the surface, even after the wood is completely dried and carefully painted. The chemicals in wood stain do the same.
Stained wood, such as the mahogany finish on the wood pictured below, is the worst culprit. Knot holes are also repeat offenders!
More than once, I’ve gone through the recommended steps for painting wood furniture: sanding, applying primer, two coats of paint AND 2-3 coats of clear finish, just to see little pink spots coming to the surface.
It’s infuriating! Sometimes it’s even large, discolored blobs from knots in the wood.
I’ve tried just about every kind of primer you can buy, even “stain blocking” primers and the only product that has yet to fail me is my old standby shellac.
Painting Wood Furniture: Preventing Tannin Bleed-Through with Shellac
I first used shellac to get a smooth finish when painting MDF, but it also makes an amazing tannin-blocking primer as well. It comes in a brush-on formula or in an aerosol can.
Shellac can be covered in any kind of finish (oil-based paint, water-based paint, lacquer, etc.).
I have started applying a coat or two prior to painting every time I’m using a light color.
It dries very quickly so you can move on to painting without losing a ton of time. It’s worth the little bit of extra time, trust me!
Note: As always, follow the application instructions on the can carefully, following all guidelines.
How to Cover Knots When Painting Wood Furniture
Now what if you just have one or two problem spots, such as knot holes?
When I built my modern bachelor chests, I primed the raw wood with BIN stain blocking primer and thought I was good. Sadly, after a couple months, the knots started to show through!
My secret weapon? Clear nail polish! 
Painting Wood Furniture: Preventing Tannin Bleed-Through with Clear Nail Polish
For a piece with just a few problem areas such as wood knots or spots that have been touched up with a stain pen or wood repair marker (which I’ve discovered is almost impossible to cover), the simple top coat you use for your manicure will do the trick!
Brush one or two coats of clear nail polish onto the areas, no need to cover the entire surface. Then fill in any gaps or indents (like around a wood knot) with wood filler.
In the sample board below, all the dark pigment is safely sealed beneath the nail polish and a first coat of paint. The indentation from the knot can now be easily smoothed over with wood filler.
Next time you pull out the white paint, remember to tackle the tannin bleed through first! A simple covering of shellac or a few spots of clear nail polish give you a simple prevention for bleed-through.
More woodwork and finishing tips and inspiration:
- How to faux stain furniture with paint
- How to use color wash on wood surfaces
- 20 DIY Furniture Makeover Projects
- 5 Furniture Makeovers
Please pin this for future reference!
Originally published 04.11.2018 // Updated 04.16.2021
Thank you! Thank you! I have a painted white “barn door” -not made by me; I am not a DIYer unless I have no other option – and I could not find an answer as to what to do about the discoloration of its sassafras lumbar. I thought I had come to the end of the internet looking for both a diagnosis and a remedy. Bless you for sharing this.
I have cabinets that I’m having a tannin issue that I’ve already primed and painted. Will either the shellac, or the nail polish, work on those surfaces, perhaps after sanding them down? I’m at a loss, and I really don’t want to have to strip them completely! 🙁
I am trying to paint a wood external door in my 95-year-old home. I’ve been told it is gumwood. I painted two coats of Kilz and the tannins are coming through. I will be using an exterior grade, water-based chalk paint as the main paint. Can I use an oil-based shellac to prime? Will water-based shellac stop the tannin bleed? Every article I read says something a bit different.
Wow, amazing. I will be using this fabulous trick. We often experience this problem when using, and trying to paint plywood. Thanks to you, we now have a solution to this problem. You sooooo rock!
Hi thank you so much for sharing about problematic wood knots bleeding through light colored paint. I would like to know what can be done after the fact- I have ship lap that I painted white, and am not getting the wood knots bleeding through. Thanks!
Hi Karen,
Thanks for the kind comment. Elisha’s nail polish trick to hide knots bleeding through will work on painted wood as well, though you may need to sand down the paint before applying the clear nail polish depending on the paint finish. (Then a fresh coat of paint on top.)