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Hard Flooring

What would cause polyurethane floor varnish to dry with tiny pimply bubbles in it?

My floor guy has had problems with both Jenkins and Ronseal polyurethane floor varnish. Tiny bubbles are left in the finish across the floor, worse in some parts better in others. He's sanding correctly and hoovering, wiping and using tac rag to be as dust free as possible. The rooms are over 10C degrees and we've sealed any drafts. He's tried 3 rooms with the same results. We're at a loss and the manufacturers have run out of ideas.

3 Answers from MyBuilder Flooring Fitters

Best Answer

It could be lot's of different things but if the floor is clean...Preparation is possibly wrong, wrong type of brush can cause air bubbles, so can very dry timber, damp timber, certain timbers react to the chemicals in certain varnishes, stirring the varnish up too much can cause bubbles...not brushing it in well enough...lot's of thin coats sanded between coats is better than a couple of thicker coats. I would say thin the varnish right down so it absorbs better and see how it goes


Answered 27th Mar 2011

have you tried sanding between coats?
we do it on every job as it doesnt matter how well you sand the wood the laqour will dry rough/prickley on the first coat.
first apply 2 coats then you need to use a light grade paper 100 g up just rub over by hand gently until any contamination is out and the floor feels smoothe then apply the third coat.
if you have tried this and it doesnt work try junkers base prime as a base coat this is quite agresive and will take well to pretty much anything.
and if this doesnt work try bona or junkers polyurethane laqours you shouldnt have any problems


Answered 19th Mar 2011

I tend to go with Restofloors with this one, I would want to know the history of the floor, for example what was used previously on the floor. Wax or Oil contaminants can sit in the base of the board and appear only when the outer surface is sealed causing the contaminant to rise to the surface area. Definitely go with a primer first before tackling the finish.
Hope this helps......


Answered 28th Mar 2011

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