Beginner's Difficulties

Behind-the-lens Shutter

(See Shutter, Behind-the-Lens.)

Bellows

An expanding and collapsible leather body provided in most modern cameras to connect the front and back portions, thus making the camera more convenient and portable.

Benzene

C6H6.

Benzol; Coal Naphtha

Clear, colorless, mobile, highly refractive liquid. Soluble in alcohol, ether, acetone, chloroform, glacial acetic acid and oils. Used in making varnishes, retouching mediums, etc. Benzin.

(See Naphtha.)

Benzol

(See Benzene.)

Between-the-lens Shutter

(See Shutter, Between-the-Lens.)

Bicarbonate of Soda

(See Sodium Bicarbonate.)

Bichloride of Mercury

(See Mercuric Chloride.)

Bichromated Gelatin

A term applied to the carbon process. Gelatin sensitized with potassium bichromate.

Bichromate of Potash

(See Potassium Bichromate.)

Bichromate of Potash Ray Filter

Biconcave

(See Lens, Biconcave.)

Biconvex

(See Lens, Biconvex.)

Binder

A gummy strip of paper used for binding lantern-slide and cover-glass together.

Bisulphide of Carbon

(See Carbon, Disulphide.)

Bitumen

(See Asphaltum.)

Blackboard Paint

(See Varnish, Blackboard.)

Black for Aluminum

(See Varnish, Aluminum.)

Black for Cameras

(See Varnish, Black.)

Black for Wood or Leather

(See Varnish, Black.)

Blacking

To avoid reflecting light the interiors of cameras, plate-holders, lens tubes, etc., must be coated with a dead-black color. (See Varnish.)

Blanchard's Brush

Made by fastening a piece of Canton flannel, by means of an elastic band, to a strip of glass or wood, 2 inches wide and 6 inches long. Used for giving plates a substratum coating, and for coating plates or paper with albumen, etc.

Roller Blind Shutter

(See Shutter, Roller Blind.)

Blistering

The formation of blisters on gelatin coated plates or paper. Caused by the unequal expansion of the film, which may be due to passing from one bath to another of different temperature or specific gravity; also, may be due to unsatisfactory coating, etc. The best known remedy is to use all solutions at a certain temperature, and the addition of a little salt to the first wash water in the case of P. O. P. If blistering is very bad the prints should be plunged, immediately after fixing, into a saturated solution of common salt.

Blisters on Bromide Paper

Avoided by adding one-half of the following solution to every 4 ozs. of fixing bath:

Sulphate of Aluminum..................................

3 ozs.

Water ...............................

24 ozs.

Shake this solution well, then allow to clear. Blistering on bromide papers may be cured by laying prints for a few minutes in a solution of

Chrome Alum.............................................

20 grs.

Water..........................................................

8 ozs.

and then in another similar solution to which 8 ounces of alcohol has been added. If blistering is not excessive, the prints may be laid in alcohol only.