Resin coming up through window cill.

[claude2]

Hi, I am restaining my conservatory, but a small section of one of the window cills has a glue like resin coming up through it. This has been the case for some time.
I have tried to seal it with natural shellac but only limited success.
I have now stripped the cill back to bare wood. Should I try again with the shellac, or use an aluminium primer, or something else?
Furthermore there are some slight ripples where I have sanded the cill slightly unevenly. The best way to remove these?
Thanks in advance from a relative novice! All advice appreciated..

 

[foxhole]

http://www.ronseal.co.uk/products/knot-block-wood-primer-and-undercoat

 

[r896neo]

I would prime it with zinniser bin. Not much will come through that and its a very useful stain block and primer/undercoat for difficult surfaces like varnish etc so useful to have.

 

[claude2]

Thanks for replies. The Ronseal product is for interior use by the looks of it. I need something that suits external, and can be stained. I will investigate the zinnniser!

 

[r896neo]

Zinniser 123 can be used outdoors but is a white paint so obviously can not be stained. Clear knotting cmpound like rustins can be stained over.

 

[claude2]

So is the clear knotting solution likely to be more effective than the natural shellac?

 

[r896neo]

Sorry i mistyped my last reply, i should have said that knotting can be varnished over but obviously not stained over. Of course knots bleeding through paint is a problem but i have never really encountered it as an issue with oil wax or varnish?