Knotting Skirting


Postby AliT » Thu Nov 13, 2008 12:51 pm

Probably a straightforward question for those in the know :idea: but I would be grateful if anyone could advise whether after staining or 'colour' varnishing bare pine skirting I can then apply knotting solution. Lots of information about it for painting but not staining/varnishing.

Many thanks

AliT
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Postby chris_on_tour2002 » Thu Nov 13, 2008 10:14 pm

you are supposed to apply knotting solution prior to overcoating, if you wanted to do it now then you would first have to remove the varnish by sanding - and if it's a coloured varnish you'd probably end up with an overlap 'tide mark' on the areas already varnished when re-applying.

treating of knots is most important when painting as the resins in the knot will cause a reaction with the paint resulting in an unsightly stain. this effect will be a lot less noticable with a varnish so unless the varnish starts to blister then i wouldn't bother to do anything, frankly. just leave it as it is.
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Postby AliT » Fri Nov 14, 2008 10:45 am

Thanks for your reply Chris. The thing is that the skirting is completely untreated at the moment as its new.

My issue is that you cannot stain knotted knots and as I need to stain the skirting I wanted to find out if it was possible to knot after staining. Otherwise I will have two different colours on the skirting.

Thanks again

AliT
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Postby chris_on_tour2002 » Mon Nov 17, 2008 12:16 am

this will probably not work very well as the stain will act as a barrier to the knotting treatment. you should always treat knots beforehand. if unsure, check the manufacturer's recommendations for the stain. it will usually give information regarding knots on the tin. if it doesn't then call the technical helpline, the number should also be on the product somewhere. in my experience helplines are usually very willing to help.
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Postby rigga » Tue Feb 17, 2009 7:39 pm

Hi there

I have found, in previous practice, that there is no need to apply knotting solution to woodwork that is to be or has been already stained or varnished, the reason, that knotting solution is only applied to woodwork that is going to be painted with oil based paint (paint that has pigment in) to stop the resin from staining the finished colour and not as I have heard suggested in previous posts to stop blistering. If there is a lot of resin is in the knot and in direct sun light it will still blister the paint, in this circumstance an aluminium based primer should be used, again only if the surface is to be painted.
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Postby chris_on_tour2002 » Fri Feb 20, 2009 9:59 am

[quote]knotting solution is only applied to woodwork that is going to be painted with oil based paint (paint that has pigment in) to stop the resin from staining the finished colour and not as I have heard suggested in previous posts to stop blistering[/quote]

I do in fact concur with your advice:

"treating of knots is most important when painting as the resins in the knot will cause a reaction with the paint resulting in an unsightly stain. this effect will be a lot less noticable with a varnish so unless the varnish starts to blister then i wouldn't bother to do anything".

and varnish, especially water based, CAN cause blistering if the knot is particularly resinous as i have experienced. in such cases knotting compound may be an option.
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Postby rigga » Fri Feb 20, 2009 7:01 pm

chris_on_tour2002
I still don’t agree with using knotting solution on timber that is going to be varnished, as I stated in my last post, spirit based shellac knotting solution should not be used for varnished woodwork even more so under water based varnish or oil based varnish because it is only used to stop staining, if it is going to blister then it will still do so. Not only is the knotting darker in colour than a clear varnish but will darken with age quicker when exposed to light than water or oil based varnish, you will then have the problem of patches of knotting showing through the finish which will look worse than the knot, ask any decorator what colour the knotting solution goes after time almost a dark nutty brown colour, and it is not water based varnish that causes the blistering its the soluble resin in the knot.
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