Use glass or plastic containers with an airtight lid. Tupperware might be the best. Pill bottles have also worked for me. Just get ones with a wide enough opening so you don't spill your cum outside the bottle. I shared with you in a pm that I like to save each load separately so the cum is exposed to air much less frequently than if you keep adding to a single container. Not as hot a visual perhaps but it may help maintain freshness. It would also help to freeze the container before cumming in it to freeze the warm cum faster. This could turn into a real science project. Whatever you decide enjoy your efforts and cum.