R. G. HARRIS

Before lantern slides have the finishing touches put to them in the way of spotting and binding, it is a wise course to put them through the lantern as soon as they are dry, to ascertain beyond doubt that the density and clearness entitle them to rank as finished slides. The constant and experienced worker can gauge with certainty the quality of his slides without seeing them projected, but the intermittent worker, especially during his novitiate, may well be excused if he fails to appraise correctly the quality of his slide. It entails very little trouble, as the slides can accumulate until a convenient quantity has been made to make it worth while arranging the lantern, and once the slides are seen to be satisfactory when projected the lantern slide worker is spared the annoyance of finding that he has finished and bound up a worthless slide.

Before masking and binding the slide it should be placed on a retouching desk and carefully examined by transmitted light for defects. Of course before making the slide the negative will have been carefully spotted and all possible defects removed as neatly as can be, but in spite of this the lantern slide will require attention at the spotter's hand from defects that have made their appearance during its manufacture. As a rule, the most that can be done in the way of retouching to a lantern slide is the removal of transparent spots by filling up with color. Knife work or any process that disturbs the surface of the film is inadmissible, as, unless most skilfully done, it shows unpleasantly on the screen. It is possible in certain cases to rub down dense portions with methylated spirit, in the same manner as is usual with negatives. But the instances when such a procedure becomes necessary do not often occur and are principally those in which it is absolutely necessary to make the best of a slide from a poor negative.

Spotting should be done by the aid of a very fine camel's hair brush and color. The precise color will depend on the color of the slide, but Indian ink and Indian red will, either singly or combined, match nearly all slides. A reading glass of low power is of very great assistance in enabling the operator to apply the color neatly to each spot. Furthermore, no light should reach the lantern slide from the back of the operator or he will fail to judge correctly the density of his spotting and find, when the slide is thrown upon the screen that all the spotting shows up darker than the transparency. The color should be kept of slightly less density than the opacity of the slide, and to ensure this being so, no light should reach the operator except that which is transmitted though the slide. The color should be used in quite a viscid condition, and tube colors are better than dry as the menstruum used in their preparation gives them a good working consistency.

As a rule, lantern slides on commercial gelatine plates are not varnished, nor does there appear to be much necessity for varnishing them, as the film unlike collodion or collodio-bromide, is not liable to be readily damaged by friction. Varnishing certainly introduces the risk of applying specks of dirt and hairs to the film along with the varnish ; on the other hand, if it is well done with a clean, hard varnish, immunity is secured from fungoid growths, which not infrequently make their appearance on gelatine films, however well defended and carefully stored. Personally, I always varnish a slide of excellent quality, more especially when it has caused me considerable trouble to prepare.

The following varnish has been spoken of in high terms far varnishing lantern slides :

Saturated solution of amber in chloroform 1 1/2 oz

Pure benzole 1 1/2 "

Gum dammar 1 1/4 "

When dissolved filter several times through cotton wool. Just warm the plate before varnishing and dry well over a gentle heat afterwards. It gives a bright, glass-like surface which is quite hard and does not become tacky.

A convenient and reliable varnish is made by •dissolving one part of dammar in twenty parts of benzole. This is applied without heating the plate and dries with a brilliant hard surface. It is advisable in varnishing lantern slides to return the surplus varnish from the plate to a second bottle fitted with a filtering funnel and cotton wool; by so doing a stock of well filtered varnish is always maintained.

Selecting a suitable mask for any particular slide is a matter that must be left to the personal taste of the worker. It is, however, not quite the simple matter it looks at first sight. Time was when a rigorous conventionality assigned a perfect circle as the only possible shape for a lantern slide mask, then dome-shaped and cushion-shaped masks began to be seen, until at the present time the decision is left very largely in the hands of the slide-maker.

It may be said that, generally speaking, lantern slides should be amenable to the same reasoning and rules that good taste and culture apply to framing of pictures. The slide mask is, to all intents and purposes, the frame of the picture, and its shape should vary with the subject in the same way that the frame of a picture is made to do. Rectangular openings will always be in better taste than the cushion or dome-shaped openings, and their dimensions should be proportioned to the subject, a very useful all 'round size being a rectangle with an opening 2 7/8|x2" Circles are useful, but of a limited application, though for many scientific subjects they are invaluable. Commercial masks are, naturally, of stock sizes, and a well assorted selection of shapes will enable the worker to select one that will suit some subject better than it would another, but not infrequently subjects will present themselves that demand a specially cut mask to frame them most satisfactorily, and the lantern slide maker must needs become his own mask cutter.

The quickest and neatest way in which to make masks of any desired dimensions for odd subjects is to cut strips of varying widths from the best black needle paper. A supply of these strips may be cut for stock of standard widths, say, half an inch, one inch, one and a quarter inches, etc. The strips are afterwards cut up into lengths of three and a quarter inches, the size of the lantern slide. With a supply of these strips and four cut accurately, it is a very simple matter to make a rectangular opening of any dimensions by simply affixing them to the slide with a touch of gum arabic or any other adhesive that may be convenient. A pair of compasses will enable the several strips to be placed equi-distant, so that on completion the opening is perfectly true. This method is very much better in all ways for the amateur mask cutter than attempting to cut a rectangular opening in a sheet of paper.

The masks should be affixed to the film side of the slide with a touch of gum and then placed under even pressure to become set in a perfectly flat condition. If when making the slide the negative is placed on the camera with its film towards the lens, the lantern slide, when looked through with its film towards the spectator, will show the subject in its correct position. Before mounting the cover glass with the slide the title may be neatly printed on the black mask with Chinese white, utilizing the right-hand end of the mask for the purpose. On placing the slide in the lantern, if the title in Chinese white be placed towards the condenser the picture appears the right way about on the screen. If the title cannot be written in white on the mask, owing to the negative being reversed when the slide was made, the slides must bear white spot to indicate their correct position.

The cover glass having been cleaned and placed in position upon the slide, the slides have now to be bound together with the gummed strips sold for the purpose.

Binding a slide is one of those apparently easy photographic operations that is a perfect nuisance until some dexterity has been acquired. Vises, to hold the slide and cover glass firmly together while the gummed strips are being affixed, may be obtained from the dealers, and they probably help the beginner, but later on he will certainly find that his fingers are his best friends.

The gummed strips are sold either cut to the length of the slide, or in sufficient length to bind around the whole of the slide in one operation. For the beginner the divided lengths are certainly the more convenient. Four of these strips are taken, the gummed surface damped (not made wet) with a sponge and placed aside for a few minutes, gummed side uppermost, on a piece of thick felt cloth. The slide and cover glass are now taken between the index finger and thumb of each hand and their lower edges placed in the centre of the gummed strip, downward pressure on the soft felt surface sufficing to attach the strip firmly to the lower edges of the slide and cover glass. On being reversed so that the edges bearing the gummed strip come uppermost, the strip can be pressed in contact with the sides of the slide and cover glass by the forefinger and thumb of each hand. The remaining sides of the slide are bound in the same manner. This is the simplest manner known tome of binding lantern slides, and I have tried a great variety, both with vises and without.

Some years ago the Photographic Club introduced a system of marking lantern slides to facilitate their being placed in the lantern so as to show correctly on the screen. It consisted of affixing two white discs of paper to the slide, on the side that gave the subject its correct rendering as regards right and left handedness when viewed as a transparency. These discs are placed at the top of the slide when it is held upright. If the slide is placed in the lantern with these discs down and towards the condenser, the view or subject is shown upon the screen correctly as to right and left-handedness. The American system of marking lantern glides is to attach one disc, known as a thumb-label, at the lower left-hand corner.