OK, that sounds like it could be the problem. Honestly, a double bath is essential. You want to melt the wax but keep it at the boiling point of water, and no hotter. As a guide to how long to keep it in the wax, the best indication is the bubbles that come to the surface.
The hot wax will expel the air in the leather. When there are no more bubbles, the leather is saturated with wax. For a flask, or tankard this can take four or five minutes. many people just dunk it in and whip it back out. It doesn't work that quick.
In fact, because you are controlling the temperature of the wax with a bain marie (double boiler), you can leave the leather in there for ages without fear of it "cooking".
I dropped a shot cup off the old wire chip scoop I use to imerse these and it sank to the bottom. I left it there while I dipped all the rest, did three tankards and some leather tablet weaving cards. I fished it out about forty minutes later and it was perfectly fine. When they were all wiped, dried and polished I couldn't tell which one had been in there the longest.
Eric
It certainly wasn't in there for five minutes - one or two at the most.
Next time I'll have the wax a little cooler and leave it in longer.
Thanks for the advice and thanks for taking the time to reply - much appreciated.