The higher standards from 60 and upwards are neutral hide glues, clear, clean, free from odor, foam, and grease.

The lower standards are chiefly bone glues, used for sizing straw hats, etc.

They are rigid as compared with the flexibility of hide glues.

For wood joints the grade should be 70 or over.

For leather, nothing less than 100 should be used, and special cements are better still.
The best glue is transparent, hard in the cake, free from spots, of an amber color, and has little or no smell.