Many thanks for applying yourselves to this one, I'm very grateful.
Temperature is 18-22C, RH 40-50% which from what I've read is within normal limits.
I've not tried brush coating yet - I'll give it a try at some point but my gut says unless I can get an even more even coating then the effect may be worse.
I put one drop of Tween into 2cc of distilled water and after a little shaking - the water, not me - I draw a single drop to add to the 20 drops of sensitizer for an 8x6. I reckon that's very roughly 800:1, Dr Ware recommends 0.1-0.2%, so that's as far as I've got exploring that variable.
Very interested that you've approximated 25 drops/cc when I've always thought it was 20 drops. Not sure whether that's going to be the difference that makes the difference, but I can experiment with that too.
To Jeffrey and the Flying Camera: Loved the picture of the boat on page 4 btw - yup, I'm with you. Once I got started I didn't have any problems with Platine either. While I've never attempted double coating, Herschel is an extremely light paper in comparison to Platine so I probably would start my experiments with the $5/sheet option.
I'm interested in the thought about pre-humidifying the paper. The paper is made from linen rather than cotton, it's not pressed in the same was as the Platine and it's about 2/3 the weight so there are a number of differences. It almost feels as though it's been retrieved from a tomb. It's hard to convey but the lightness and thin-ness (?) of the paper almost suggests a prehistoric dryness and humidity that's far lower than that of the room in which it's been stored.
Many thanks all. The next action for me is to try pre-humidifying the stuff, probably over a tray of warm (40-50C) water - what's the concensus(sp): 3-5 minutes?
I'll let you know how I get along,