I thought I'd jump in here for a moment.

All of the comments here are useful and understandable. The coating technique is crucial!!!

My assistant, Madelyn Willis and I or coincidentally are doing a silica demo at Christopher James' workshop at the Santa Fe Workshops tomorrow.

As I have said in the notes on the process, there are a ton of variables to test, and we will learn more from the field use than attempting to test a million different ways to use the material.

Some thoughts.

Most likely you will need a good paper to start with and one that will handle some extra brushing of the the sensitizer.

We have found that roller coating of the silica works best and eliminates the extra drying step.

The key is getting enough, but not too much silica, on the paper. If the roller is fully charged and has been used for a number of prints, then around 1/2 teaspoonful to an 11x14 sheet is about right but this is going to end up being more of an intuitive issue with the worker. (It's art!)

The key is, after roller coating the silica, to brush the sensitizer on rilly rilly well. OK, now my hearing is shot to hell, so when Maddy is with me during the coating she says she hears the brushing start to squeek with each brush stroke, which is done at the end, lightly and briskly. A very high pitched squeek comes with the brushing. That may not happen with all papers but it does with COT and Platine.

Streaks in the final print are likely:

Too much Silica or Alumina
Too much senitizer -- at first it doesn't seem as if you have enough but it does tend to spread out as you coat.
Not brushing long enough, you need to go to the matte stage and then more. At least till it squeeks and then some. It is strange but it seems like you really need to brush it in.

So I suggest starting with a small amount of silica, being careful not to get too much sensitizer on, enough, but not where it gets sloppy, and brushing the print until it is matte and then squeeks, and then some.

--Dick Sullivan