Not Knotting

[michael]

Having recently paid an exorbitant price for a bottle of knotting, I was dismayed to discover that the product is no longer of any use to me in this modern day paint world. The notes on the back of the knotting bottle advise :-
“Not suitable for over coating with paints containing alcohol solvents. Please note that many water based and water miscible paints contain alcohols”.
Seeing that all modern paints appear to be going down the water based and presumably alcohol based road (Including my paint) What is the modern day alternative to knotting?

 

[plasticpigeon]

Does water based paint need knotting as a prep? How about using an oil based primer and then water based topcoat? Probably not much help eh. I'm sure someone will have experience of this.

 

[TheForge]

Shellac and linseed oil based paint?

 

[michael]

I believe wood knots will bleed through water based paints so I guess they still need to be sealed. Knotting followed by oil based primer then water based top coats sounds like a good solution but I suspect that oil based primers will also eventually disappear from the market. I love the idea of linseed and shellac based paints but I’ve never got round to using them and I imagine they’re not really practical for the average d.i.y.er let alone the modern day professional painter, where drying times may be an issue.

 

[steveb]

shellac seems to dry pretty quickly (it dries by the alcohol evaporating off?) but not sure if you could use that under "other" paint

We're using shellac under linseed oil paint ourselves , the linseed oil definitely does not dry quickly

 

[Flyfisher]

I don't understand why a water-based paint wouldn't work over knotting. Once the knotting is dry isn't the remaining shellac pretty inert?

I guess the only way to find out is to try it on a piece of similar test wood.

 

[michael]

The producers of the knotting must know what they are talking about to put this note on their bottle. I guess that alcohol must dissolve the knotting? It seems therefore that even shellac based paints containing alcohol (according to ‘steveb’) would also be unsuitable. That leaves linseed oil paints which is a far too long a painting process for me.

 

[Flyfisher]

I know what you mean but there must be some way of sealing knots that is compatible with modern paints. Let's face it, only a tiny percentage of paint customers are going to bother with linseed paint.

I wonder if the knotting manufacturer is just trying to cover themselves because I thought the whole point of modern paints was to reduce VOCs, so it seems strange they might still contain enough alcohol to dissolve the shellac from knotting.

Most DIY manufacturers have a technical helpline. I would call the knotting manufacturer and ask them the question. I would also call the manufacturer of the proposed paint and ask them how to seal knots in new wood.

Do, please, post their answers here though!

 

[Penners]

I don't understand why a water-based paint wouldn't work over knotting. Once the knotting is dry isn't the remaining shellac pretty inert?

I guess the only way to find out is to try it on a piece of similar test wood.

I agree. In fact, I have used water-based paint over knotting compound on a number of occasions without any discernible problems. But I suppose it depends on whether the paint does, in fact, contain alcohol.

Like FF, I would try a test piece.