wood knots

[invalid.address]

Hello,

I have bought odd bits of architrave and skirting board in the past that have had knots in them. I've primed and painted them and they haven't caused any problems... yet.

I've never used knotting solution; should I have done?

I've tried to google to find out more about it but I am getting conflicting advice: some web sites say treat all knots regardless but others say only treat weeping knots. Is that why I've been fine, because mine weren't weeping?

Another site says that they can take years to weep and they might look fine now but play-up later. Is this true?

What about black knots? I was taught to avoid wood with them in. I presume that knotting solution won't save them?

Do I have to use a special primer on top of knotting solution? One web site said you must always use an oil based primer on wood, yet so many primers are water based. All multi surface primers seem to be water based and crown wood primer is too, though dulux is not.

Does the base of the primer make a difference?

Are all knotting solutions equal or are some better than others?

Thanks.

[The Natural Philosopher]

I used water based acrylic primer over knotting. No probs. I just knotted as a precaution.. no idea if its necesssary or not, but its cheap enough so why not?

I would say they are all pretty much equal, frankly.

[The Medway Handyman]

I did the same with a door frame & the knots started to show after a few years.

I always though all knots shouls be treated.

With my door frame yes.

I've always used any old primer over knotting.

I'd always assumed they were much the same.

[Stuart Noble]

Traditionally based on shellac, which is only soluble in alcohol. The resin that oozes out of knots is soluble in white spirit and hence oil based paint

[invalid.address]

So that would explain why the instructions say to wash your knotting brush in meths, not white spirit. It would also mean that there is no advantage in using an oil based primer. Thanks.

[Andy Dingley]

Don't bother washing it. Just wipe the thick off it, then next time you go to use it, a spot of meths beforehand will soften it.

My knotting solution is home made - shellac sanding sealer. Get some cheap shellac from somewhere with a good turnover of stock (Screwfix's button shellac) and dewax it yourself. Leave it to stand undisturbed for a week, then gently pour off the top 2/3rd as "best" and leave the stuff with the visible cloudy wax in it behind. Use this as sanding sealer and knotting. You might usefully add about half as much meths to it. I get through a ridiculous amount of shellac - I use it for everything, from waterproofing cardboard to thread-locking fountain pens.

For brushes, go to a cheap artshop / remainder bookshop for illiterates and buy a artist's _synthetic _ watercolour brush. A 3/4" or 1/2" filbert shape is about right. These are ideal for shellac.