Old Brown Glue is fresh “hot” hide glue in a bottle. The liquid glue is made from hydrolyzed collagen and urea in small batches - literally made to order! Each bottle has a "Best if used by" date which can be extended if kept in a refrigerator. To make “hot” glue, the manufacturer recommends heating the glue by putting it in the sunlight or a warm water bath for a few minutes, and we concur. This completely organic, nontoxic formula has a 30-minute open time and requires 24 hours to dry completely.