Can you tell us more about it?

Nice work.

Thanks! Yes I'll reply with details soon!

Papier sepia or sepiaprint is a process that was invented by Rudolfo Namias. It's similar to the vandyke brown process but uses citric acid instead of tartaric acid. Sepia paper has been used commercially for purposes similar to blueprints. The process is very simple:

make up solution consisting of:
20% ammonium iron citrate ( aka ferric ammonium citrate or ammonium ferric citrate! )
5% citric acid
5% silver nitrate

add the silver nitrate last and let any precipitate redissolve
wear eye protection and nitrile gloves when handling silver nitrate

coat paper, let dry.
expose until midtones just start to show
wash for a few minutes in water
fix for a few minutes in weak hypo ( sodium thiosulfate )
wash for 10 or 15 minutes in water

the image will intensify in the wash again in the hypo.

For these photograms I've been using a variation, and fixing them in
5% sodium sulfite for about 5 minutes ( instead of hypo ). This makes a more yellow image and Namias says it is better for use as a negative... but it's also quite pretty.

Namias' original article is very enjoyable to read. I've uploaded it here to Ipernity if you are interested in reading it:

Preparation of Papier Sepia

My simple way of making these is as follows:
use little eyedropper bottles with:
A. 25% AFC
B. 12% citric acid
C. 24% silver nitrate

in a little disposable cup, mix drops 2:2:1.
for example 20 drops A, 20 drops B, and 10 drops C.
mix only as much as needed to coat papers.

This approach lets you use the eyedropper bottles for other purposes like salt printing or VDB.

There is also a thread with more information about this process at Photrio

fixing the image with salt instead of hypo makes a very interesting golden color. I might try that soon with one of these photograms.

I highly recommend trying this process, it's simple and fun and not prone to failure!

Looks like an autumn leaf on slate, beautiful colour contrasts. I bet it’s more complicated than that, but it remains simple, serene, contemplative. A kind of icon.

thank you!

Indeed, a little like alchemy...
I like the blue tone as well.

Thank you for the information.