[sdiy] PCBs from printouts

[Hugo Haesaert]

Hi Jim n All !

>Back when I used to do my own PC boards, there was some stuff made by
>GC called "transfer it", or something like that.  It was supposed to 
>be used to extract PC board film from printed magazine pages.  I 
>never tried it .  I am not exactly sure how it works (or, if it did 
>indeed work at all).

Don't know who or what GC is .  But i am familiar with a kind of 
graphic film called reflex film .  It is based on a (formerly ?) 
patented process and produced by Gevaert (belgian photo company, 
bought in the 60s by Agfa, became Agfa-Gevaert, the name Gevaert was 
subsequently dropped) .  It produces straight positive copies from 
positives thru the use of of a physiological developer, that develops 
the non exposed silver halides iso the exposed ones .  The non 
developed silver is then removed by fixer, same as always .  The 
reflex part comes from the peculiar way this film can be exposed .  
The light goes through the film ;-) 

If a darkroom and some hard or extra hard paper is available, one can 
experiment with this .  Put emulsion against print, and do not forget 
to place a black sheet of paper between the next pages, lest the 
reverse shows through ( a good trick for photocopying too btw :) )  A 
graphic or very hard developer is best used for these experiments .  
These will of course not yield positive but negative images .  
Exposure is kinda touchy .

There is some more to this reflex film, but it's been ages, and all 
this is from memory :) (can you tell i studied photograpy ;^) ) (in 
the '70s)

I still must have the remains of a box of this film .  Gave very 
good, sharp results, but had to be copied on regular graphic film 
sometimes, as the density of the black was at times marginal due to 
the lack of contrast in the original .  Electuur/tor uses pretty 
white paper, but ETI/PE/Everyday electronics/EMM used a kind of thick 
newsprint that yellowed quite fast, hence... (retouching plays here 
too...)

In EU this film was marketed by Seno in the Electronics circuit
(is ?/not distributed anymore in BE) .  But 15 A4 sheets cost as much 
as a box of 50 10x8' sheets from Agfa ;)

Bye for now .


Keep 'em oscillating :)


Hugo
=