en years
before he, or rather his backers, gave up. He tried mixing in various
things to stiffen up the pyroxylin. Of these, camphor, which he tried in
1865, worked the best, but since he used castor oil to soften the mass
articles made of "parkesine" did not hold up in all weathers.

Another Englishman, Daniel Spill, an associate of Parkes, took up the
problem where he had dropped it and turned out a better product,
"xylonite," though still sticking to the idea that castor oil was
necessary to get the two solids, the guncotton and the camphor,
together.

But Hyatt, hearing that camphor could be used and not knowing enough
about what others had done to follow their false trails, simply mixed
his camphor and guncotton together without any solvent and put the
mixture in a hot press. The two solids dissolved one another and when
the press was opened there was a clear, solid, homogeneous block
of--what he named--"celluloid." The problem was solved and in the
simplest imaginable way. Tissue paper, that is, cellulose, is treated
with nitric acid in the presence of sulfuric acid. The nitration is not
carried so far as to produce the guncotton used in explosives but only
far enough to make a soluble nitrocellulose or pyroxylin. This is pulped
and mixed with half the quantity of camphor, pressed into cakes and
dried. If this mixture is put into steam-heated molds and subjected to
hydraulic pressure it takes any desired form. The process remains
essentially the same as was worked out by the Hyatt brothers in the
factory they set up in Newark in 1872 and some of their original
machines are still in use. But this protean plastic takes innumerable
forms and almost as many names. Each factory has its own secrets and
lays claim to peculiar merits. The fundamental product itself is not
patented, so trade names are copyrighted to protect the product. I have
already mentioned three, "parkesine," "xylonite" and "celluloid," and I
may add, without exhausting the list of species belonging to this genus,
"viscoloid," "lithoxyl," "fiberloid," "coraline," "eburite,"
"pulveroid," "ivorine," "pergamoid," "duroid," "ivortus," "crystalloid,"
"transparene," "litnoid," "petroid," "pasbosene," "cellonite" and
"pyralin."

Celluloid can be given any color or colors by mixing in aniline dyes or
metallic pigments. The color may be confined to the surface or to the
interior or pervade the whole. If the nitrated tissue paper is bleached
the celluloid i