The details are
much the same as above, and necessitate double transfer.
After the picture had been obtained on the plate (ordinary glass plate),
and after thoroughly fixing, washing, and toning, the picture (and this,
remember, is the case likewise with terra-cotta) then has to be loosened
from its support, and this is done with a solution of sulphuric
acid--one drachm to fifteen ounces of water--which is made to flow
between the image and the glass, after which perfectly wash and mount.
When the image is loosened a piece of tracing paper is put on the image,
evened out, raised (assisted by some one else to hold the two opposite
corners during the operation), and with the aid of the helper the
picture is carefully centered, gently pressed out or down, and the
transfer is so far effected. But what will happen, and does happen,
in the case of vignettes, is impurity of the whites, when the picture
becomes positively objectionable. Now the way to remedy this lies simply
in the application, to the dirty-looking parts, of a solution of iodine
dissolved in iodide of potassium to sherry color; after which, well wash
and apply a weak solution of cyanide of potassium, and wash well again.
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