Since you achieve a good polymerization in the tube where you prepared the solution the problem could be in the glass plates, perhaps the plates could have grease. I always clean them with ethanol before use and handl them by the edges. It could be a possibility..

I agree with the answer of Maria Luisa. Also I want to add that

1. Polymerization is dependant on the temperature. If it's cold in your lab, the process will take more time, especially in thin layer between glasses.

2. In some tutorials it is mentioned that deoxygenation of stock solutions with nitrogen will speed up polymerization. I usually skip this step because my gels polymerize, but always it takes more time for glasses than for leftovers in tube. But I'm trying to avoid bubbling during mixing of stocks.

Hi Debora Ruf !

I agree with Alena Balashova

1) Try to use fresh PSA 10% . Make sure you mixed well your acrylamide with PSA and TEMED before pippeting.

2) You can use a ultrasonic bath or vaccum pump to acrylamide degaseification if you dont have nitrogen.

3) Use ultrapure water and check your buffers (concentration and pH).

Best,

Jacó