(46) 
The Ordnance Survey Department uses four different methods of printing. 
Their photography for revision of town maps at a photographic scale of 1:2,500 
is printed on a Kodaline emulsion supported on Kodak Topographic base film. 
The printer is a Zeiss rectifier type SEG 1. The temperature rise of the negative 
in this rectifier has been found to be appreciable and has been reduced in one unit 
by using cold cathode lighting. Prints are hand processed in trays and dried 
on racks in this and in the following three processes. Photographs for mapping- 
rural areas at a contact scale of 1:7,750 are prepared on bromide emulsion on 
Kodak foil card base. The contact printer used has a point light source at 6 to 
8 ft. away. It uses as a pressure pad a metal pressure plate from an air camera. 
Some rectified enlargements are also made from these same negatives to give a 
scale of 1:2,500; the procedure is similar to that outlined for the first process. 
For the coastline photography prints are made on Kodak bromide paper with 
the Zeiss type SEG 1 rectifier. For the photography carried out for revision of 
small scale maps, prints are made on Kodak bromide paper using a box type 
contact printer with diffused light. A sponge rubber pressure pad is used in 
these printers and bad contact is apparent by a loss of definition. The temperature 
rise in these printers is also known to be considerable and it is planned to replace 
these printers by the type using a distant point light source. 
Remaining printing procedures involve bromide emulsion on double weight 
paper or aluminum foil. The Williamson POC printer with a surfaced cork 
pressure pad has been tested with a fine reseau negative and has been found to 
give satisfactory contact if a few seconds delay is given between lowering the 
pad and making the exposure. Temperature rises as high as 10°F have been 
found on prolonged printing. 
Finland 
Prints are made on bromide or gas light (chloride) paper. For the prepara 
tion of rectified prints a Zeiss rectifier SEG 1 is used. With an f :6• 8 lens it has 
a scale accuracy of 0-1%. The rectified prints are made on wet paper and used 
while wet with glycerin 27 . Contact prints are also made in printers which use 
rubber pressure pads for sizes below 18 x 18 cm and vacuum devices to ensure 
contact in larger sizes. 
France 
All prints of the IGN are made on bromide paper. French materials used 
are Kodak Pathé, Guilleminot, Lumière, Crumière, As de Trèfle, etc. Belgian 
Gaevert paper is also used. It has been found that the five grades of paper 
generally manufactured are not sufficient in many cases and it is desirable to 
decrease the interval between grades by using papers from various firms. Glossy 
papers are usually used and these are dried without being glazed. Partial tests 
have shown that the resolving power of the glossy bromide papers is quite 
adequate. 
The sensitometric tests used for papers consists of exposure to a standardized 
wedge and exposure to a series of 10 aerial negatives of progressively varying 
contrast. 
Tests have been made of the dimensional stability of various papers. Re 
sults are given in the following tables.