This is a platinotype example of the use of Fumed Silica. I posted this in the alt forum here but wanted a more generally accessible example as well.
The image on the left was a normal pt processed print, the image on the right was enhanced (imo) by brushing on fumed silica to the paper before applying the metals emulsion.
Please post more if you have them Robert, very interesting. Had watched video with Richard Sullivan making Athenatype just a couple of weeks ago. The process is very interesting, will have to pick some up and investigate as soon as I can find some darkroom time. Richard explains that the D-Max is enchanced.
I bought my FS off Amazon, it was $12 and shipping for enough to last me a lifetime.
Dana (Sullivan) thinks it keeps more of it on the surface which allows it to have a "thicker" emulsion. I'm still trying to decide if that's true due to an increase in contrast (about a grade, guessing) or if more emulsion would just change the speed and/or cause fogging.