Stain block

[gemshan1]

Hi guys, I recently installed a new staircase, I’ve painted it with water based acrylic primer undercoat and then a quick dry satin, yes you’ve guessed it a couple of months later the knots are bleeding through! Do I need to rub back to bare wood before applying a stain block or can I apply it over what’s there at the moment? Also I’ve been told to just use a oil based undercoat instead on a more expensive stain block but not to sure about that suggestion... which stain block would be best? Thanks

 

[opps]

You could use one of the pigmented shellac based paints to spot "prime" over the knots.

Eg Blockaid by Smith and Rodgers or Zinsser BIN. Both are as good as each other but the former costs less.

No need to sand back to the knot.

Edit, use a throw away brush or clean your brush in household ammonia.

 

[gemshan1]

Just a thought, I have quite a few tins of left over auto paint, ie cellulose etc, surely this should block anything in its path? Not being tight just can’t be arsed to que up at screwfix lol.

 

[opps]

I guess that should be fine. Never tried it though.

 

[DiyNutJob]

Not being tight just can’t be arsed to que up at screwfix lol.

Sounds tight. Queue at screwfix is never this bad.

When you say bleeding through, are you talking about sap? If sap, best to let it bleed out. Get to the knot, clean the sap with white spirit, degrease with washing up liquid, then prime and paint. Water paint is fast. No need to use blocker.

 

[opps]

Sounds tight. Queue at screwfix is never this bad.

When you say bleeding through, are you talking about sap? If sap, best to let it bleed out. Get to the knot, clean the sap with white spirit, degrease with washing up liquid, then prime and paint. Water paint is fast. No need to use blocker.

I have spent 30 minutes in queues at screwfix in the past.

If you have a particularly resinous knot, it needs to be drilled out/pulled out.

Shellac is not guaranteed to prevent knots becoming visible over time but it is far, far more effective than waterbased paint alone.

I paint skirting boards as part of my living. Small knots, yeah I ignore them and use acrylic primer, larger ones I use shellac.

It might be helpful if you let people asking questions know that that your anecdotal experience is very limited. When responding I often try to let them know that I am providing anecdotal advice (sometimes I fail to do that though, but in my responses to electric/plumbing related questions, I will preface my answer by saying that I am not a plumber/electrician/etc).

 

[DiyNutJob]

It might be helpful if you let people asking questions know that that your anecdotal experience is very limited.

Anecdotally, you want me to say the stuff you say. It is better for you to let other people to say what they want to say. My view is that it is better to do simple things than do complex things that might not even work. Sap is best let out than to allow to build up. In a DIY setting, on an easy to access location, a quick clean up and repair is sufficient, and no queuing at screwfix is necessary.

A blocker allows a "tradesman" to buy time to get away. A DIYer does not face the same issue. If the repair fail, he can go redo it in a jiffy.

 

[Wayners]

Fitted my pine stairs in 2008 and used knotting solution but it failed. Knots started to show around 2012.
So I coated the entire lot in aluminium primer.
Left it a week then 2 coates of acrylic primer undercoat.
Two coats of water based satin.
It worked.
If I was to do it today I'd probably do the same again.
A bit overkill tbh but it's a sure thing.

Probably your easiest option is 3 spray cans of zinsser BIN.
Warm them in hot water and spray the lot. Don't take long Vs brush and roller.
Acrylic primer undercoat
Denib
Paint two top coats. As a DIY person that's your best bet

 

[opps]

Anecdotally, you want me to say the stuff you say. It is better for you to let other people to say what they want to say. My view is that it is better to do simple things than do complex things that might not even work. Sap is best let out than to allow to build up. In a DIY setting, on an easy to access location, a quick clean up and repair is sufficient, and no queuing at screwfix is necessary.

A blocker allows a "tradesman" to buy time to get away. A DIYer does not face the same issue. If the repair fail, he can go redo it in a jiffy.

What are you on about?

Most knots are tiny and do not seep any noticeable sap. Those kinds of knots have been sealed with shellac for hundreds of years.

If you have very resinous knot, yeah, you can remove the dripping sap with white spirit but on the balance of probability, it will continue to weep, hence my recommendation to remove the knot.

Your rant about tradesmen makes no sense. A tradesman that doesn't care about longevity would follow your advice and not bother using any knotting solution.