The ribbon may be tanned or hardened by soaking in solutions of chromic salts. Greater the concentration of chromium salt, slower will be the digestion of the gut in the body. Thus, tanning causes a delay in the absorption of the gut in the body.

Terms such as plain, chromic and extra chromic are used to approximate the absorption time of the gut in the body. Plain gut is digested by enzymes at a faster rate than chromic gut. Deficient tanning may result in its premature absorption.