***DO***NOT***ADD***FORMALIN***TO***DEVELOPERS***O R***FIXERS.

Now that I have your attention, there are some cases you can do either or both. Some lith developers use formalin and some non-ammonia fixers use formalin. In these cases, remember that any amines or ammonia present will react with Formalin, so Metol will react as will a PPD developer. Ethanol Amine and Diethanol Amine will react with Formalin. Ammonium Hypo will as well.

If you are going to play with this, you have to know some chemistry.

PE