"Having, in my earlier experiments on the collodion process of photography, experienced some difficulty in always producing a collodion of uniform quality with regard to sensitiveness, tenacity and fluidity, although making use of the same materials for its preparation, and this I find being the complaint of many others, it has been my study lately to determine the variations in quality to which the ingredients are liable, and the effects of these variations on the sensitive film, and likewise to ascertain whether the excellent qualities of some samples of collodion depend on the materials in ordinary use, or on some substances accidentally or intentionally added. Researches in the preparation of collodion may appear superfluous, now that it is supplied of the best quality by so many makers; but as some persons of an independent turn of mind still prefer manufacturing their own, I venture to bring forward the subject with the hope of benefiting them. In this beautiful process so much depends for success on the quality of the collodion, that when in possession of a good specimen, it becomes one of the easiest and most simple, and ought to be the most certain of all the processes yet devised; for here no material of uncertain composition is introduced, such as paper, and thus we have nothing to fear from plaster of Paris, alumina, or specks of iron or copper, which continually endanger or modify the calotype process; each ingredient can and ought to be obtained in a state of perfect purity, and with this precaution the degree of success depends upon the skill of the operator himself.