This is now in stock at Silverprint in the UK. There are a couple of types but it is the "Bromoportrait 80" paper which is recommended for 1st pass lith.
I tried some of this yesterday:
Sensitivity: Broadly comparable to IMGWT, so I found a standard print worked at 30secs @ f5.6 on my enlarger.
For lith I added two stops to the exposure, extending to 1'30".
Developer: For the test I used my standard mix of Moersch Easylith @ 1:40
The developer exhausts pretty quickly, compared with say FOMA paper.
Reaction to the developer is initially prompt but quickly tails off, as follows:
Print 1. Faint image at 5'40". Pull at 8'50"
Print 2. Faint image at 7'26". Pull at 11'30"
Print 3. Faint image at 14'50". Pull at 33'00" - developer effectively exhausted. I have yet to try replenishment or "old brown".
Tone: Printed to a warm slightly greenish brown tone. The tone cooled as the developer exhausted. Paper shows good infectious development but the Dmax is quite low.
Yet to try 2nd pass lith and toning.
I've posted yesterday's 3rd print of the Leeds Canal.
I also tried unibrom last weekend but on my homade classic formaldehyde developer:
Faint image, Pull: Lith
3.- 8-16 (excesive slow, replenished at 10' with HQ an Sulfite)
It's depends of the components used and its concentration, i made two changes to get maximun black... Also if BP Slavich paper has additives a prewash could help
I have not tried this paper for lith, but it may be useful to reduce the amount of sulphite in developer to increase DMax.