Neither, Lex. "Rapid" means that it contains ammonia - either as ammonium thiosulfate or as added ammonium chloride. It can be acid, neutral or alkaline.Originally Posted by Lex Jenkins
I use my own recpie, an alkaline buffered solution of sodium thiosulfate and ammonium chloride. Works faster and is less smelly than TF4, which I tried for the first time last week. I'm going back to my own version. Details will be posted as soon as my test print has been taped to the window for a year without fading.