RA-4 developer

Description

The colour developer for optical printing on modern paper. It is used up faster than the BLIX, which is why it is sold separately.

Why temperature matters here

RA-4 runs at 35 °C, and it is the developer that sets the colour balance of the print. A degree out shifts the balance visibly — keep the tray in a water bath through a session, or the last sheets will not match the first.

How long it lasts

Diluted developer oxidises quickly, especially in an open tray. Mix what one session needs and keep the concentrate in a full, closed bottle.

Questions and answers

My prints drift in colour by the end of a session — why?

The developer is exhausting and cooling. That is normal RA-4 behaviour; hold the temperature and refresh the solution.