Milky or Cloudy Varnish:
If your varnish has not dried totally clear - Itís cloudy or milky; then the simple answer is that it is not dry underneath. Water
based varnishes dry incredibly quickly. If you put them on too thickly the top layers of paint
will be dry to the touch. You think it is time for the next coat and away you go. The trouble is that layers of varnish under the top layer have not dried. The moisture has not had a chance to evaporate properly and now there are more layers on top preventing this process from taking place. It follows that if water
is trapped in the varnish it will remain milky or cloudy. Water can be trapped in the film of varnish in a number of ways: recoating a varnish before it is dry, application of a thick coat, or the top drying too quickly. Varnishing in summer sometimes means that you have to take the temperature conditions into consideration.
The first step is leave it for a few weeks and see if in curing the varnish clears. If not sand it back with a piece of 1200 wet and dry sand paper and sand with a little water. Let this dry thoroughly and start over. Avoid the problem this time by applying thin layers and allowing the varnish to be really dry. The time depends on the actual varnish you are using, so read the manufacturers instructions and follow them carefully.
When the water evaporates the "whiteness" goes with it.