Never any hassle with either frames or foundation until this last season. I always bought only from Th*rne from the time I started, up until last year. Around 2% losses with second quality frames
This last season brood:
The frames were Th*rne seconds and losses were a little up on the normal approx 2% (usually weak lugs, but some too-large dead knots this time around).
The foundation was from K*S which fitted neither this year's frames nor last year's.
Th*rne foundation from last year fitted the Th*rne frames OK (both of previous and this years purchase as well as some third party frames of unknown origin supplied in a new hive, but new and assembled. Not sure whether I have any of the 'unknown origin' frames left to compare the two foundations, but I did try the different foundations in the same frame, as a control test.
The super foundation was perfectly OK, but the 14 x 12 was simply not square (or rectangular) enough. All foundation was stored in the same place and under similar conditions, as it has been for the past ten years.
There have been reports that some of the Th*rne winter sale foundation was out of square also.
Working your way through that carefully may allow you to draw conclusions which may seem certain or possibly less so. I have my ideas.
So no reliable method except getting read-built frames with foundation fitted, and checking them for squareness (before using, and finding the bee spaces are incorrect at different points!
I have bought from Okehampton and their foundation smells divine and fits my poorly made frames very well BB, super and even 14x12 - and the frames are poorly made because I make them...better luck next year...
You can buy ready made ones from Thornes for an extra cost. But surely it is not too taxing to put them together yourself- they normally fit fine and are easy to make (even for an incapable craftsman like me).
Thornes beeswax conversion where you pay a little money works out to be a better deal.....the more wax you have the cheaper the rate...but 10lb of wax plus £10.80 would get you 80 sheets of standard brood foundation..unwired...£8.40 more if you wanted wired.