BURNISHER (Fr., Pressed satiner a chaud ; Ger., Heisssatinirmaschine) A machine for imparting a glossy surface to prints by pressure and friction against a heated and polished bar or roller. The bar burnisher A —the older type—has a polished steel or nickelled must be avoided. The prints should not be quite bone dry, and if kept too long they do not burnish so well. On the other hand, they must not be damp, or they may blister and stick to the bar or roller.
When a bar burnisher is used, the prints will require, before burnishing, to be lubricated by rubbing with a mixture consisting of 4 grs. of castile soap dissolved in i oz. of alcohol, applied with a tuft of cotton-wool. To dissolve the soap, the bottle containing the mixture is placed in hot water. The print is passed through the burnisher face downward, pulling it upward in a. slightly curved direction from the back as it goes through. This is done three or four times. When the print is passed through flat, without pulling it, whether in a burnisher or a rolling press, hot or cold, the operation is known as " rolling " • but this term is frequently applied indiscriminately to burnish ing also.
With a roller burnisher, 4 lubricant is not required. Solid rollers take some time to get hot and require to be rubbed lengthwise with a soft cloth until heated, meanwhile revolving the roller backwards ; this is to prevent the deposi tion of condensed moisture from the air, due to the lower part of the machine getting warm first, while the roller is still cold ; this moisture, if allowed to settle and dry on, would make the roller dull and streaky, and might cause rust.
The more modern burnishers have a hollow roller with the gas burners inside it ; this gets hot in a much shorter time, and the heat is also bar and merely a single roller ; while the roller burnisher—or, as it is sometimes called, " enam eller " B—has two rollers, one or both being of polished nickel. The bar burnisher is said to give the better gloss, hut has the disadvantage that the prints need lubricating, and they occa sionally get scratched. Both kinds are heated by spirit or gas, or with hollow rollers steam is sometimes employed. Rolling presses, properly so-called, have a large flat steel plate and a single polished roller, and are used either with or without heat.
Burnishers of agate or other stone have had in the past a few photographic uses. (See" Agate Burnisher.")