I made a video that explains all this: jump to the bottom to watch. Also, see the last section labeled “Caution”.
Don’t use just any primer or you will be sorry!
Tree knots are full of resin that bleeds through low-budget primers and all paints. They simply don’t have the solids that block wood resin stains.
Not sure? Here is a post on every kind of stain and the primer you need.
The ONLY primer that works here has a “shellac base”, and that means alcohol is the solvent. Even oil-based will allow knots to bleed through.
White-pigmented shellac is what you want.
The correct primer in this case
You need to spend a bit more, (quite a bit) but you don’t need to use a lot of primer.
I use two products interchangeably. They are both great for nasty stains. They both stink, literally.
1. BIN, shellac base. Comes in two sizes. For DIY painting, a quart is probably best.
Because a gallon can go bad if you don’t seal the lid perfectly, I buy a gallon with some empty quart or gallon cans. Ha! (don’t use plastic or glass … don’t ask)
DO NOT BUY the “synthetic shellac”. It’s water-based and it will not work on tree knot stains. (Learned this the hard way).
2. Kilz, shellac base is the same as BIN.
If you can find it grab it. It’s often out of stock. I see it nowhere online right now.
Again, you don’t use much so it really lasts a long time, UNLESS you don’t seal the can well. So I buy a gallon and 3 empty quart cans.
Tip for these nasty primers
These primers’ solids settle fast so after the initial shaking you will need to re-shake or stir well (and stirring this is nasty).
How to seal tree knots
- Shake well (a paint store will shake it for free)
- Open your quart or gallon
- Pour off what you need in your work bucket and close the lid
- Keep the lid tight when you are not pouring and your supply will last
- Leave an air gap and your primer will be solid in no time
Read the label to find the solvent. If it “cleans up with water”… avoid it. That’s ok for other types of stains, but not the nasties.
Look for ‘denatured alcohol’ or just ‘alcohol’. I use rubbing alchol to clean up. Bing. Done.
(Water stains are almost as tough so I use shellac on them too.)
Caution #1
Careful: there are water-based types.
Don’t get “SYNTHETIC SHELLAC”. It won’t work for nasty knots.
Caution #2
Wear a respirator and ventilate around these products. They are toxic. Not nuclear dump toxic, but toxic.
Here is the final paint job:
and here is the bottom of the bottom with an unsealed knot. In a year I’ll re-photograph this and we’ll see how the stain bleeds through!
Any questions? I’ll be watching.
I have just finished a ceiling in knotty pine. I had hoped to white wash it rather than put on a solid paint but I still want to seal the knots. I want to be able to see them through the white wash but not have them bleed through. Is there a Bin product that would work for this?
Thanks!
Not sure what you mean. You want to see knots? But you want to seal them?
I think you might mean you want to see the wood, but knots contain resin that come thru any whitewash or paint.
They will not bleed thru a good primer like shellac based BIN or Kilz.
Water based BIN is not as good and will let knots bleed thru, but this may take time…sometimes years to bleed through.
Thanks Brad!
Yes, I want to be able to see the wood grain and also the knots. But I do not want the knots to bleed resin, or awful yellow tint and goo through the whitewash look.
The Shellac based Bin that is in my Home Depot says it is white. I have never used it before, so I am assuming that this white shellac would be a solid cover on the knots. That is, using the BIN white shellac would cover up the knot entirely rather than simply seal it from bleeding goo. Is this correct? Or, is the white BIN shellac just a slight tint that allows me to still see the knot?
For the final whitewash look, I am thinking I need to shellac the knots with clear BIN shellac and than apply either a whitewash pickling stain or a whitewash watered down latex paint. Does this make any sense at all?
Problem is I cannot find any BIN clear shellac (like the white product in my home depot?)
Yes It will cover entirely (shellac)
If you want to see the rest of the wood, don’t use that primer. Just cover knots. Should work fine.
You won’t find BIN clear. Never heard of it. Other shellacs would work. But test that!
I highly recommend testing whatever you do in spots!!!!
Thanks for the helpful information on painting pine knots. With needing to use the shellac primer, what type of paint can you use to paint over it? I’m thinking you can’t use a latex water base. Thanks for any further help.
Any paint can go over this and generally, all primers. Latex is fine
Dear Brad, I recently painted my loft, which has knotty pine, in two layers of water based zinsser allcoat, not realising that it doesn’t have a knot blocker in it. I can just about see some knots coming through already and Im worried that if I spot prime I wont see all the knots that havent yet come out. Would I be okay to put a coat if zinsser bin shellac on the whole thing and then repaint in a water based paint?
you are right: spot prime. I often do this: prime with run of the mill primer and go back with shellac. WHy? I’m cheap. and the shellac is so toxic. Plus, I’m cheap!
You have so much good advice! 🙂
I have just finished staining 4 large exterior carriage doors with a solid acrylic stain from Cabot.
The pine knots have just started to bleed through.
Will bin or kilz shellac work to stop this or at least slow it down even though I’ve already put an acrylic stain on?
I have dealt with this issue many times before and (very stupidly) forgot to prime first with a shellac this time around.
Yes, but only workable if your stain is “solid” which is basically paint. Then yes, use Bin or Kilz ALCOHOL based, not water based. The water based is not for tough stains…just heavy primer. Good luck!!
Countless thanks! I did it all wrong last summer – water based primer and paint . All the knots poked through. About to redo- using shellac this time. (-;
I have to repaint the knot with BIN twice before o stops coming through. Is this norrmal?
If it is the alcohol based BIN, yes, if the water based, not really. Depends on what your stains are. And remember over time stains work thru some paints if not sealed. My advice, even tho I have no idea what you are doing…is to buy a quart or gallon of BIN w/ alcohol (very nasty stuff) and hit the spots that bleed thru. Read on my site about this product: use a brush you will throw away, respirator is key, etc.
Good luck
Thank you! Thank you! Thank you! the mystery known as pink spots reappearing on a painted wood framed mirror is solved. I’m so happy I found you Brad. now on to the ‘fix’.
What if the board is painted and the knot bled through? Do I have to sand the knot before applying bin? Am I risking bleed thru if I don’t sand before applying bin?
Not a big problem. Sanding optional probably but I cannot see it! Just spot prime with the Bin… Shellac based bin, not water based will seal any knot. The other stuff is good for most things and much less smelly
Good luck!