This section is from the book "Cassell's Cyclopaedia Of Mechanics", by Paul N. Hasluck. Also available from Amazon: Cassell's Cyclopaedia Of Mechanics.
If it is required to make a vignette photograph without showing much dark around the head and neck proceed thus. Cut in cardboard (old plate boxes answer well) a vignette considerably smaller than the desired vignette G (Pigs. 1 and 2), and fix about 3/4 in. from the negative by fastening with drawing pins. To do this, it may be necessary to nail some strips of wood B around the outer edges of the printing frame. Fig. 1 shows a perspective view and Fig. 2 a section of the vignetted frame. Cover with cotton-wool A any thin portions of the negative coming near the margins - such as may occur with a black coat - or the light will creep too far and the shape of the vignette be spoilt. The wool must be pulled out very loose and soft, or a hard line will be shown by the shadow it casts on the negative. In cases where the negative is very thin it is advisable to cover the vignette with tissue paper. Vignettes should always be printed in subdued light. A vignette card must not be cut too closely around the figure, nor its outline repeated too decidedly, as the effect thus obtained will be quite as inartistic as the stereotyped egg shaped patch. To produce a successful vignette, a light background must be used. With a dark background it is all but impossible to get a soft vignette. The farther the hole is from the plate and the darker the background of the negative, the larger will the vignette be, and the softer will be its outline. During early attempts at vignetting the print should be examined from time to time to see that the vignette is going on satisfactorily.

Fig. I.
Fig. 2. Vignetting Photographs.
 
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