View Full Version : Sizing paper

02-16-2012, 10:06 PM
Anyone know any instructions or formulas for sizing paper with gelatin using chrome alum as a hardener? I'm going to be sizing for salt prints and I've searched everywhere online on instructions or recipes and haven't found anything specific. Any info would be great!


Andrew O'Neill
02-17-2012, 12:19 AM
Make a 2% Chrome alum solution:
•Hot distilled Water 500 ml
•Chrome Alum 10 grams

Mix until well dissolved

Then in another container:
•Hot distilled water: 750ml
•Gelatin: 7 grams
•2% Chrome alum solution: 20ml
•Distilled water to make: 1 liter (total)

You can re-warm for a few days and then you will notice a strong smell.

02-17-2012, 01:16 AM
I've seen this formula during my searches online, but found it lacked specifics. For instance, what exactly is the process for coating the paper, is there a certain waiting period before applying the salt print chemistry? What is the sizing supposed to look like on the paper? If you have any personal experience, please share. Other than that, I've already searched far and wide for answers. Thank you for the reply though:)

02-17-2012, 05:01 AM
Chapter 15 of Christopher James' "the book of Alternative Photographic Processes" is an excellent guide on sizing.

02-17-2012, 06:57 AM
Be aware that chrome alum takes a few days to harden the gelatin completely and it also gives the paper a faint bluish cast.

Photo Engineer
02-17-2012, 11:40 AM
A blue cast, IMHO indicates too much chrome alum.

Here is my formula:

Make up 10% gelatin (weight / weight) by using 10 grams of gelatin in 90 grams of water.

Add to that up to 5 ml of 10% chrome alum or 5 ml of commercial glyoxal at 4% (40% diluted to 4% with water). Chrome alum will take up to 2 days to harden, but glyoxal is done in about 4 - 8 hours.

Add 0.5 ml of surfactant such as 10% saponin, Photo Flo 200 or just plain Ethyl Alcohol (Everclear sold in some liquor stores).

Apply this mixture at the rate of 12 ml / square foot or less (not more) to the paper by any of the common methods such as brush, dip, coating blade etc...


02-17-2012, 01:12 PM
So do you allow the mixture of gelatin and chrome alum to sit for the 2 days to harden? Or do you coat the paper and let that sit for 2 days?

Photo Engineer
02-17-2012, 02:51 PM
Once you add any hardener to gelatin, the clock is ticking. It must be coated ASAP. Sorry, I thought that was obvious, but some people don't do this every day like I do.


02-17-2012, 02:54 PM
So then what is the waiting period you spoke of then?

Photo Engineer
02-17-2012, 03:05 PM
Once you coat the gelatin is not immediately hard. It can wash off the paper when you process it. You have to wait for any hardener to react and that takes hours or days depending. You should not coat on top of the sizing for that same amount of time so that the coating layer does not ruin the sizing layer.


02-17-2012, 10:58 PM
The concentration of gelatin required for single-coat sizing is very much dependant upon the paper, and its intended use. A heavy coat of 10% gelatin will likely completely seal the paper surface, whereas a more dilute mixture can retain some of the paper 'grain' but prevent staining/excess penetration. The amount of sizing ideal for a gum print is not the same as for a carbon-transfer, or salt-print, VDB etc.,

Be prepared to experiment! :D

Photo Engineer
02-17-2012, 11:10 PM
Very very good point Ian.