I have often had different results using the same solvent cement from one kit to another. I suspected that maybe the exact mix of the styrene may be different. Some of my friends say this is definitely true. Anyone know for sure how much variation there is in styrene used, from one mfg to another? Doesn't seem to be very much variation in how well CA sticks to parts, but sure seems to be variation with solvent cements and epoxies.