Varnishing disaster

[sailorman]

It doesn't matter what wood it is really Simon especially if its solid. Sanding if you have the thickness will eventually get you to virgin wood. Good luck!

By the way what I didn't say was that all wood darkens when subjected to UV. Light sanding often gives you light patches and dark patches because you are breaking through the UV affected surface. If you have the thickness don't "tickle" it. Use a course grit paper and take the surface off removing up to 1mm material if necessary, then reduce the grit until you remove al scratch marks. I have just done an area on my boat (complete refit on a new to me boat) Started with 60 grit and followed with 80, 100 and finally 120 by machine before one coat of 50/50 varnish. Then when hard 120 again but this time by hand using a wood block to "flat" down, (sand with the grain when finishing) followed by 4 coats of gloss with 10% thinners, then flat down again and give a final 2 coats of ready rubbed (matt) The result is superb but it takes hours of patience!!

Not forgetting to warm the varnish in a kettle of hot water before use to thin without thinners therefore keeping a fuller bodied product

 

[boatmike]

Not forgetting to warm the varnish in a kettle of hot water before use to thin without thinners therefore keeping a fuller bodied product

Yes indeed this can help if it's very cold weather but don't overdo it. Some varnishes will dry very quickly if too warm and you want a slower drying time to maintain a wet edge and allow brush marks to flow out. Also too warm and you drive off the solvents making it even thicker!

 

[lotusman]

Years ago (about 40) use of nitromors used to be associated with a deep purple staining of mahogany, the instructions contained a warning to this effect. It smelt different then, and I haven't been able to track down any current warning but who knows?

I've never had much luck with getting a good finish after using a heat gun for varnish removal, I can't seem to get all of the remnants of old varnish out of the grain.

 

[Jcorstorphine]

Use white spirit first

I always wash down the wood after sanding with turps / white spirit as it will show up any areas which have either stains or residual varnish.