having probs with getting loads of air bubbles in what should be the final coat of my varnishing.

tried brushing slow – better, tried fast – as bad, but still happening badly and so not happy with the finish. anyone have any tips?

thin it down a bit. Is the coat below sanded down to proper flat and cleaned?

Dry.
Warm ambient temperature.
Clean with Tak-rag , Tack cloth.

cleraned down nicely, but freezing cold erring on damp room.

cold and damp

most spray workshops and boat sheds are kept warm and pos dry for a reason. I’ve tried putting varnish on outside when cold a few times (on boats), didn’t work very well. Wait for warmer times or warm/dry the room first.

are you using a heater at all and when do the bubbles appear, straight away or minutes after application?

yes there is a heater in the room but it does nothing for the underlying chill, you freeze through.

bubbles appear pretty much instantly.

Ok try brushing it on, leave it for a minute, then lightly drag the tip of the brush over the surface to break the bubbles, any drag marks should dissappear (assuming oil based). They usually occur when air is trapped and expands from heat, or using a roller, or if you were over enthusiastic with the stirring beforehand and made the varnish frothy. Rubbish brushes wont help either, i like Hamilton perfection for varnishing.

All the above refers to an oil based varnish, if you’re using water based crap then your on yer own 😉