I had a clay at one time and had the same experience. You can put some petroleum jelly on the stem to keep it from sticking to your lips. Back in the day, they painted the mouthpiece area.I have had confirmation that both my orders are on the way. The samples, and the two new pipes. Hopefully I will see both by the weekend.
I'm fairly confident that I'll be aborting on the clays. To be honest, I only wanted the satisfaction of solving their riddle, not keep them long term. Aside from possibly being useful while I work through the samples, they're not much use to me. They don't sit, are awkward to hold, and the unglazed stem can stick to my lip if I don't keep them wet. If the next smoke isn't satisfactory, they're of no use to me for exploring the samples and will be thrown away.
Moving forward, I already have a dedicated pipe each for English, aromatic, and lakeland. I also have two pipes that I'm happy to smoke anything in, and a 9mm filter pipe for toning down overwhelming flavours. That leaves me three that are as yet unsmoked. I believe the only other family I ought to dedicate a pipe to is Virginias/Periques, but if anyone thinks there's another family of blends I should keep separate, please let me know.