Guncotton in an air-dry state, whether in the original form or after grinding to pulp and compressing, burns with very great rapidity but does not detonate unless confined.
As the quantity of contained water increases it becomes difficult or even impossible to detonate by an ordinary blow.
A small charge of dry guncotton will, however, detonate the wet material, and this peculiarity is made use of in the employment of guncotton for blasting purposes.
The liquid when soaked into a porous combustible substance like blotting-paper burns rapidly and quietly, and when struck with a hammer on a hard surface violently detonates; when a little of the liquid is spread on an anvil and struck, the portion immediately under the hammer only will, as a rule, detonate, the remainder being scattered.
It is very difficult to detonate by percussion.