I needed to make a repair on some PVC pipe. When I opened my can of cement, I discovered that is was thicker than when new. I purchased the cement around a year ago and kept the lid firmly closed. The can is about 2/3 full. I could still easily spread the cement around the pipe. At what point is the cement no longer viable? Can it be made viable by thinning it with PVC primer? Yes, I should go purchase a new can of cement.