Will knots bleed through varnish

Johnboy54 · 19 Apr 2021

Hi to all.
About 10 years ago I made a pine kitchen.
Few years later the wife wanted the doors white.
I didn't do any knotting, never thought, so obviously knots are now showing through.
She wants it painting again.
I originally used Dulux gloss, then 2 coats of Ronseal Diamond hard varnish.
The doors are moulded and grooved, and it was a pain sanding them down to start with.

My question is, will the knot stain be bleeding through the varnish?
I can obviously see the stain but I don't know if it can get through the varnish.
It'll save me a load of hard sanding graft if it can't.
Roughing it up is a lot easier than removing it.
Many thanks,
John

opps · 20 Apr 2021

Sorry, I don't quite understand what you want to do.

Do you want to paint them white again? If yes you can just spot prime the knots with a shellac based paint (eg Smith and Rodgers Blockaid or Zinsser BIN). If the knots are resinous and bubbling up, you will have to consider pulling them out/drill them out. You do not need to sand all the way back to the wood before applying the shellac paint. Alternatively, you cn use regular knotting solution. It will be cheaper but because it is clear you might find it more difficult to apply it evenly.

Johnboy54 · 21 Apr 2021

Thanks for that opps.
My laboured point was...

Yes, I'm painting them white again.
Will the varnish be sealing in the resin?
Is the varnish acting as a sealant already?
It's Diamond Hard so it's supposed to stop stains getting through the varnish to the paint below.
Does that also apply to stains/resin coming out?

I just want to get away with hard sanding entire sections, as I'm assuming just knotting the affected parts will show up as a patch when I paint over it.
I've already bought 2.5 L of Zinsser 123, which just needs a light sanding of the varnish according to their site.

I can see the resin through the paint below but can't see any coming through the varnish.
Not that it means it's not coming through I suppose.

Thanks.
John

opps · 21 Apr 2021

I would not expect the Ronseal to prevent bleed through, nor would I expect the 123 to stop it either. The only product that Zinsser seem to recommend is BIN. Unfortunately, the smallest tin of BIN is £16, a 1L tin is only £2.5 more. The cheapest option will be a small bottle of knotting solution at £5ish for 125ml, which should be enough for your needs.

https://www.screwfix.com/p/liberon-knotting-solution-natural-pale-125ml/

Use a decent quality brush and dip it in smelly household ammonia before washing it out. A couple of quid for a bottle but you can pour it in to a jar with a lid to stop the ammonia evaporating off.

Johnboy54 · 21 Apr 2021

Thank you very much opps.
Looks like that's my only option.
I was going to get the BIN but when I read the drying times, and the fact it stinks, I decided against it.
Thanks again.
John

opps · 21 Apr 2021

BIN smells because the solvent is alcohol.

I have painted whole rooms (walls) with it in the past. Yes it probably smelled like Hogarth's Gin Alley but a soon as the paint dries, the smell is TOTALLY gone. On a warm day, the smell is gone in about 40 minutes- and that was 40 squared metres. You are looking at 0.001 square metres(?).

From memory, the total cure time for BIN is about 3 days, but the total cure time for water based paints is up to 10 days and up to a month for oil based paints. You can paint over BIN in 20 to 30 minutes. It is the fastest drying single component paint that I am aware of. The fact that it dries so quickly is the reason why I only use it for spot priming when working with wood.

BIN is pigmented shellac suspended in alcohol. Knotting solution is un pigmented shellac suspended in alcohol.

Johnboy54 · 21 Apr 2021

Right...
I'm probably taking the 123 back and getting BIN.
It was the warnings for safety with BIN that put me off.
VOC, masks, well ventilated, headaches, nausea etc.
I'll be taking the doors off and painting them one at a time in my small shed.
Looks like getting a full bodysuit!
Thanks again,
John

opps · 21 Apr 2021

Slow down...

I am not recommending that you paint the doors with BIN, just the knots (and if you don't want to pay the premium for BIN, use knotting solution).

I have no idea what you have read but I spent many years painting MDF cabinets, some of which were wardrobes. Most of the time they were hand finished in oil based eggshell. In the case of 5m of wardrobes, I could easily spend 12 hours just painting the interiors. BIN stinks but it smells of alcohol, AFAIK it is not harmful (given the limited time exposure to the evaporating alcohol). In comparison, the smell from oil based paints in close proximity is unpleasant and definitely not good for you, and it lingers for days.

You seem to sensitive to, or concerned about paint smells. Stick with the 123 but use a shellac based finish just for the knots. If you can walk in to a pub without fainting, the small amount of shellac based BIN or knotting solution should not present a problem.

Johnboy54 · 22 Apr 2021

Firstly, many thanks opps for taking the time to explain things to me.

I've ordered the BIN from Screwfix, which is where I got the 123.
I'll return the 123.
As I said, I wanted BIN originally because Zinsser say that can go straight on varnish without sanding.
Just a good clean.
And it sorts the knots out.
Alcohol has been my friend for 50 years, so if I'm painting in the equivalent of a pub I'm all for it!

One more question -
I've used water based paints for years, as it's easy to clean brushes.
But at the end of each day I wrapped brushes/rollers in cling film and they were good to go the next day without cleaning.
Would BIN need brushes etc cleaning each day or would it stand a night in cling film?

Thanks again,
John

mattylad · 22 Apr 2021

I found it easier to just use a cheap brush and consider it a throw away item after use.
They did not like the cling film trick.

Could always buy the cleaner but ISTR that the cheap brushes were far cheaper.

My reuse/recycling acquaintances would be disgusted with me - lol

opps · 23 Apr 2021

As Matty says, cling film doesn't work that well. that said if I know I will be using the brush the next day I do store it in a plastic bag over night. If it has started to go slightly hard, I just coat it up with more BIN, it will soften up after a few minutes.

If you accidentally leave it for a week or two, the ammonia will still clean it.

Johnboy54 · 23 Apr 2021

Thanks to you both.
I'm sorted now.
Just got back from screwfix with the BIN exchange.
Just need some motivation now in glorious weather like this.
I think I'll start Monday.
No time like later on.
Barbecues instead I reckon.
Many thanks.
John

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Will knots bleed through varnish

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