Most specimens, such as animal and plant tissue, can be stored for a long time in concentrated alcohol. The alcohol will remove the water from the specimen and preserve it. Some specimens, unfortunately, do not respond well to the treatment with alcohol. they start to shrink and deform. You can reduce this effect by first placing the specimen into 50% alcohol for several days and then to concentrated alcohol.
Specimens which are dry from the beginning do not have to be stored in alcohol. This includes animal fur, textile fibers and the like. Keep them dry until they are mounted. As a general rule, if the object is able to decay under normal conditions, then you should store it in alcohol, otherwise it is not necessary.