Instantaneous Pictures may be taken by employing the iodide of iron in the collodion. The best method with which I am acquainted, is to have a saturated solution of iodide of iron in alcohol, and drop one or two drops into an ounce of the collodion (which has been previously iodized) used in taking positives. This can be used at once, as soon as mixed. No more of this collodion should be prepared than is wanted for immediate use, as it will keep good for only a few hours. The saturated solution of iodide of iron can be kept on hand ready for use at all times. There should be an excess of the iodide in the alcohol. The same accelerating effect is produced with the negative collodion prepared in this way.
Plain Collodion may be iodized as soon as dissolved: this will save time in settling. It is a fact that some cotton is more readily dissolved when the bromo-iodizing is present: but by the addition of this, I have often taken up considerable quantities of the gummy sediment remaining in the bottom of bottles.
Prepared Glass may be preserved clean and free from dust by keeping in boxes such as those used for keeping daguerreotype plates. By taking out every other partition between the grooves, the glass can be readily put in.
Collodion Vials and Bottles, after having collodion in them once, should be rinsed with alcohol and ether (in the same proportions as employed for dissolving the cotton), before using them a second time for that purpose. Penuriousness in this respect would be bad policy.
Coating Large Glasses.—A convenient method of doing this is represented in the following illustration:
The glass is held by one corner, 2; the other corner, 4, is rested on a table or bench, and the collodion poured on, so that the excess may be poured off at 1.
Black Stains upon the hands, caused by nitrate of silver, may be removed by moistening them and rubbing with a lump of cyanuret of potassium. This salt is poisonous, if used to a great extent [See [page 139]]. Another safer, but more expensive plan, however, is to take a saturated solution of iodide of potassium in water, and then wash with nitric acid diluted with two parts water.
Stains upon White Linen can be removed by washing with a saturated solution of iodide of potassium containing a little iodine; then wash with water, and soak in a saturated solution of hyposulphite of soda until the yellow iodide of silver is dissolved.
The hands should always be washed after fixing a positive or negative picture, before again touching a glass to be coated, or the dipper; this precaution is necessary, lest any of the iron salt, or the hyposulphite, should get into the silvering solution and spoil it.