If vellum is stored in an environment with less than 11 % relative humidity , it becomes fragile , brittle , and susceptible to mechanical stresses ; if it is stored in an environment with greater than 40 % relative humidity , it becomes vulnerable to gelation and to mold or fungus growth .
If vellum is stored in an environment with less than 11 % relative humidity , it becomes fragile , brittle , and susceptible to mechanical stresses ; if it is stored in an environment with greater than 40 % relative humidity , it becomes vulnerable to mold or fungus growth .