If working an old battery, never renew very strong, or it will work dark and heavy. A battery, to work well, should be gradually losing strength, but never gaining.
An old battery, however, may be quickened up and made to work well for some time, by adding five of six drops of sulphuric acid, repeating the quantity as often as necessary, providing always that acid be not used in manufacturing the quick.
4. Have the plates lost their sensitiveness by being many times exposed to mercury? Clean and burn them; but if French plates, burn light, or you spoil them.
5. Are the buff s dry and clean? Examine the plate critically after buffing to detect any appearance of scum or film on the surface. If so, the longer you buff the more it shows.
Scrape and dry the buffs thoroughly.
6. Is the mercury free from scum and dirt? If not, filter.
Is it also far enough from the coating boxes? Should be at least three feet, and kept covered.
7. Is the mercury sufficiently heated? This is important.
Long exposure, however, will answer the same purpose.
8. Are your lenses clean, and in proper place?
9. Are the tablets in focus with the ground-glass? If you can attribute the failure to none of these, mix a new box of some other kind of quick, say the dry, for instance. If you fail in the same manner here, take time, wash your buffs, overhaul all the chemicals, and start anew.
Do not be discouraged.
There is no day so dark but that the sun will shine again.
We will close with this brief summary of advice:
Clean your plates. Keep everything dry. Keep the mercury hot.
Follow these instructions carefully, and you must succeed.
HINTS AND CAUTIONS.
First of all, cleanliness should be observed. When there is dust or dirt about your room, particularly about the work-bench, failures will be frequent;for the smallest particles of rotten-stone, when allowed to come in contact with the buffs, will produce scratches on the surface of the plate, which very much injures the operation, and often causes failures.
Dust flying about the room is injurious, if allowed to fall on the plate, either before or after it has been coated, as it causes black spots which cannot be removed.
The polished plate should not be allowed to come in contact with a strong current of air, for it tends to oxidize the surface.
Breathing on the surface should also be avoided, for the same reason.
The plate should, in all cases, be buffed immediately before using, and not allowed to stand any length of time.
It should be held with the polished face downward.
It is always best that the plate should be of the same temperature of the atmosphere in the room.
Keep the camera and mercury-bath perfectly free from the vapors of iodine and bromine; for the presence of the slightest degree of either of the above will injure the impression in no small degree.
As a preventive, let the camera be exposed to the sun or fire for a few minutes in the morning.
Filter your mercury often, to keep the surface free from film and dust.
The hyposulphite solution should be filtered through sponge every time it is used.
The direct rays of light must not enter the camera in conjunction with those reflected from the object; or the picture will be veiled, and the color of the plate changed to a thick green.
If the plate be iodized only to a light-yellow, the result might be of a bluish or grey tinge: and this is generally the case, when the quick is new and strong, and there is an excess of it on the plate, and yet not enough to form the bromide iodide of silver;in which case it would wholly spoil the impression.
Your iodine will be found to operate more successfully, when the time required for coating the plate does not fall short of fifteen seconds, or exceed one minute.
Too quick coating can be avoided by using less iodine in your box.
In the summer months, when the weather is 80 deg. and over, one quarter of an ounce, or even less, will work to advantage.
ELECTROTYPING.
I am indebted to Mr. J. H. Fitzgibbons for the following process, which he employed in producing the excellent specimens he exhibited at the Crystal Palace:
"I shall endeavor to lay down in as comprehensive a manner as possible the method by which I have been enabled to produce the most satisfactory results.
I use a Smee's battery (another kind will do). After filling the cell, of common size, nearly full with water; add about quarter of an ounce of sulphuric acid. Mix this well, and let it stand for about three hours, or until the action of the battery becomes weak, when it is in order to work with a very uniform action. Put one pound of sulphate of copper in one quart of water; stir it until the sulphate of copper is all dissolved, and then add one half ounce of sulphuric acid and a quarter of an ounce of nitric acid.
This solution, well mixed, should be filtered, and it is ready for use.
It is very important that the solution should be kept clean, clear, and free from all foreign substance. The above quantity of this solution will be found sufficient for electrotyping a dozen of the sixth-size plates.
When it is required to be strengthened, it is only necessary to add a little of the sulphate of copper.
"With the battery prepared as above, and the solution of sulphate of copper in a vessel of proper dimensions to receive your plate, connect the galvanic current, and immerse the impressioned plate, letting it remain until a thin film of copper has been formed, then the battery can be strengthened, and the impression will be of sufficient thickness to be removed in from eight to twelve hours.
An old Daguerreotype plate attached to the opposite pole of the battery (copper side towards the face of the plate to be electrotyped), will answer the same purpose as the silver-plate.
"The great difficulty in taking an electrotype impression, and preserving the original, has been attributed to the battery being too powerful.
