Frozen clean urine may be the new way to go. On April 4th 2011 I got clean piss from a friend who stop smoking about a year ago. I froze the pee in quick fix bottles I had laying around. To freeze the pee I used a turkey injector set used for injecting turkeys to fill the bottle from the collection cup. After the bottle was cap off I wrap the bottles in tin foil then put the bottles in freezer bags. I heard its better to use a vacuum sealer to seal the bottles but I don’t have one if you do I would go this route. After its wrap in tin foil and put in the freezer bags I just placed it in the freezer. Make sure your freezer is set at a lower level. Good way to check is put ice cream in your freezer and see it develops ice crystals. If it develops ice crystals then its to cold. Well the pee went in on 4/20/11 I took out one sample today to replace it with a new clean one and check it with a piss test strip. Ph, specific gravity and creatinine came out fine. It still had a nice yellow color and have a low foam head. It also still had a smell. so if i had to use it today i would of been fine.To reheat the pee put it in a glass of hot water. Then to heat it up use hand warmers.If your in a hurry use hot air from your car on way to site. DO not microwave real urine it will kill it making it test low on all levels.hope this helps.im still usin gf for test also but nice to have a back up plan!