Printing process for alcohol labels?

Homebrewing husband and I use gelatin as glue (because it comes off easily to reuse) and spray shellac over the printer-paper label for a modicum of waterproofing. However, our biggest batches are about 50–75 bottles – probably not totally practical for a run of 20K. (That must be quite a fermentation vessel!)

Contact your commercial printer. They will show you all available stocks and explain what the pros and cons are of each. They will also be able to tell you about the glues and any extra steps like varnish or foiling. You are not expected to know the particulars of all papers. When you are speaking with them, ask them what they need from you to make a successful file. The may need particular things that they will have to create if you haven’t. That will increase your charges, and make it less certain that you get what you expect. They usually are willing to explain all steps to you. If they aren’t, just write down what they have said and ask me. I can explain.