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.
[Photo below] I came across your website while trying to do some research on fixing a trim bleed through issue. I built a modular home about 7 years ago. Everything has been great with the quality of the build, etc with the exception of the interior trim. It was delivered primed and we had it finish painted locally. From the start we have experienced significant bleeding on the trim. The modular company acknowledged it, said they had seen it with some other house built in the same timeframe and attributed it to a bad batch of trim they used which was probably rushed and not ready to be used. They had guys come down and repaint and then it started again about 2 years later, it was during covid, impossible to get anyone to come, so I sanded a bunch of areas, primed it, and repainted, and it has all come through again. I used a primer that my local paint shop recommended, but I don’t believe it was oil-based because I remember it having no significant smell and it washed off pretty easily. I am seriously rethinking replacing all of the trim, but was curious if you think a good sanding and an oil-based primer will fix this? It is virtually in every room of the house.
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Thank you,
I would not accept that explanation. I would write back and tell them THEY need to come to your house and fix all the bleeding knots. They should know to use stain-blocking primer on SPF (spruce pine fir) for obvious reasons.
RUSHING? No. SPF needs sealing. No amount of time would prevent this. Only Shellac.
Your fix is not so bad: Kilz or BIN shellac, not the water-based stuff, but the alcohol-based stuff. Water-based will block some but not the goey resins in pine etc.
I’d hire a painter, send them the bill with the number of your lawyer. They should GIVE you that trim for free..
Good luck
b
Brad!
I painted an old pine armoire a few years ago; did not know about bleed and hence used no primer. The other problem is that I antiqued it as well as used a sealing top coat on it.
Now what do I do? Both the paint and antiquing have aged; getting a fix to match the original paint will be difficult if no nearly impossible. Am I looking at a total redo?
Yes, redo, but it’s not as bad as all that. The pine will keep bleeding so you need to use the shellac based primer (alcohol-based, not water based) BIN or Kilz. Sand every square mm of the sealer you have on the top: this is for ‘bite’ or bonding. Then primer, then your preferred color. If you want, sure, sand it all off down to the wood. It CAN be done. If you are worried about many layers building up.. But it’s pine. It is not Louis 14th.
Good luck!
b
Hi Brad,
I feel you’ve answered this across the various comments I’ve read and I’ve found the information to be really helpful but I want to ask again in case I make a mistake!
I’ve spot treated my knots with Liberon knot sealer (shellac based) its goes on sort of clear. I saw you spot treated in your video with the white tinted sealer too – I’m painting interior wood walls, completely untreated spruce which I’ve then used a preserver on for bugs/rot and then knot sealed. Can I base coat the wood with any regular primer/undercoat now I’ve spot treated the knots or do you recommend using something like Zinsser Cover Stain Primer (oil based) and stick to something meant for wood and not regular plastered walls?
Really I’m trying to be cheap but I don’t want to cost myself more in the long run, so if I have to go for something proper like Zinsser I will!
Thank you – Rebecca (DIYer commenting from Scotland!)
Thanks for your time!
Hi. You can keep costs low but too low and you’ll have so many problems later. It never is a good deal to use bad products. That clear sealer looks fine: White is just a plus. Main point: yes , use a good oil based primer, but not necessarily for stain blocking which costs more. But you need adhesion, and painting wood is tricky. SPF, spruce pine fir are sappy and you need to be careful. Buy your primer, test a spot, let dry and try to scrape it off with your nails. Should be ok with the Zinsser you mentioned. Let me know!!
B
Scotland!!?? I just wrote a song about Scotland!!! I’ll send link by email…not ready to record yet, but very soon.
Thats great!
Thanks for getting back to me so quickly. My dad often said “do it cheap, at best do it twice or at worst do it thrice”. Comparing differnt kinds I’m definitley going to get the Zinsser with the stain block, its got a seriously short time between recoats (2hrs) compared to the 16-24hrs of most other brands, paying £20 more I get the convenience of the job being done in a day + stain block benefits. Win win!
I’m might be bias but I’d say Scotland is worthy of having songs about it!
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!