Chloride ('Gaslight') Silver Gelatin Emulsion
'Gaslight' emulsion is probably the simplest of all silver gelatin emulsions to make. It's a chloride-based emulsion giving a neutral tone with deep rich blacks. It is very slow and quite contrasty and is well suited to contact printing.
When it comes to making it you don't need a whole lot of equipment, although it does make life a lot easier if you have access to a magnetic stirring hotplate. If you don't you can make it by heating the emulsion in a waterbath and stirring it with a small plastic whisk instead. Apart from that you need some measuring beakers, scales, plastic spoons, an eyedropper, a thermometer, and a timer. Finally, you'll need a lighttight container to store the emulsion in once it's been made, a red safelight, and a room that can be blacked out in which to make it.
Ingredients wise you'll need distilled water, potassium chloride, photo grade gelatin, silver nitrate, standard strength plain vodka and some wetting agent (Kodak Photo-flo or similar).
To Make
You can make a batch of this emulsion in a couple of hours, but most of that is waiting time so you can get on and do other things. Go into your blacked out room, put the lights on, and:
1) Add 135ml of distilled water to a beaker. Dissolve in 3g of potassium chloride. Add 25g of gelatin and give it a gentle stir.
2) Let the salted gelatin solution stand for 30 minutes to allow the gelatin to absorb as much water as possible ('bloom'). Meanwhile:
3) Add 25ml of distilled water to another beaker. Dissolve in 5g of silver nitrate. Silver nitrate stains everything it touches so be careful. Do not let it get anywhere near your eyes. Read the MSDS for it.
4) When the 30 minutes are up put the salted gelatin on the hotplate. Set the hotplate to warm the solution to 50°C and leave for 30 minutes to warm up, melt, and stabilise.
5) Add a stirring bar to the salted gelatin and start a vigorous but non-splashy stir. On my hotplate I use a fairly short bar and set the speed to 800 rpm.
6) Set a timer for 10 minutes. Turn on the safelight and turn off the main lights.
7) Slowly trickle the silver nitrate solution into the salted gelatin, midway between the edge of the stirring vortex and the edge of the beaker. The mixture will turn white as silver chloride is formed. Continue stirring until the 10 minutes are up.
8) Stop the stirring but leave the beaker on the heat. Turn off the safelight and let it sit for 30 minutes in complete darkness.
9) When the 30 minutes are up switch the safelight on. Gently still in 35ml of plain vodka along with 10 drops of wetting agent.
10) Either wrap the beaker in a lightproof bag or pour it carefully into a lightproof container. Store in the fridge.
Coating
The emulsion seems pretty robust and can be melted and cooled numerous times with no real impact apart from a slight speed increase. Coating needs to be carried out in safelight conditions.
To melt the emulsion warm it to 40°c. I use a soft brush to coat, spreading the emulsion out quickly and then finishing by going over the surface slowly and gently with the brush to remove any air bubbles. Paper wise I've never had any problems with this emulsion, as long as the paper can stand up to being processed it should be fine. I find Saunders Waterford works best for me. Peg the paper up to dry in complete darkness then store it in a lighttight bag.
The coated paper keeps well. Contact print it under a bare bulb - I use a 150w tungsten bulb at a distance of a metre or so and get exposure times around 20 seconds. Processing is in normal black and white chemicals, just being careful with the paper surface which will be delicate when wet.
Chloride ('Gaslight') Silver Gelatin Emulsion
'Gaslight' emulsion is probably the simplest of all silver gelatin emulsions to make. It's a chloride-based emulsion giving a neutral tone with deep rich blacks. It is very slow and quite contrasty and is well suited to contact printing.
When it comes to making it you don't need a whole lot of equipment, although it does make life a lot easier if you have access to a magnetic stirring hotplate. If you don't you can make it by heating the emulsion in a waterbath and stirring it with a small plastic whisk instead. Apart from that you need some measuring beakers, scales, plastic spoons, an eyedropper, a thermometer, and a timer. Finally, you'll need a lighttight container to store the emulsion in once it's been made, a red safelight, and a room that can be blacked out in which to make it.
Ingredients wise you'll need distilled water, potassium chloride, photo grade gelatin, silver nitrate, standard strength plain vodka and some wetting agent (Kodak Photo-flo or similar).
To Make
You can make a batch of this emulsion in a couple of hours, but most of that is waiting time so you can get on and do other things. Go into your blacked out room, put the lights on, and:
1) Add 135ml of distilled water to a beaker. Dissolve in 3g of potassium chloride. Add 25g of gelatin and give it a gentle stir.
2) Let the salted gelatin solution stand for 30 minutes to allow the gelatin to absorb as much water as possible ('bloom'). Meanwhile:
3) Add 25ml of distilled water to another beaker. Dissolve in 5g of silver nitrate. Silver nitrate stains everything it touches so be careful. Do not let it get anywhere near your eyes. Read the MSDS for it.
4) When the 30 minutes are up put the salted gelatin on the hotplate. Set the hotplate to warm the solution to 50°C and leave for 30 minutes to warm up, melt, and stabilise.
5) Add a stirring bar to the salted gelatin and start a vigorous but non-splashy stir. On my hotplate I use a fairly short bar and set the speed to 800 rpm.
6) Set a timer for 10 minutes. Turn on the safelight and turn off the main lights.
7) Slowly trickle the silver nitrate solution into the salted gelatin, midway between the edge of the stirring vortex and the edge of the beaker. The mixture will turn white as silver chloride is formed. Continue stirring until the 10 minutes are up.
8) Stop the stirring but leave the beaker on the heat. Turn off the safelight and let it sit for 30 minutes in complete darkness.
9) When the 30 minutes are up switch the safelight on. Gently still in 35ml of plain vodka along with 10 drops of wetting agent.
10) Either wrap the beaker in a lightproof bag or pour it carefully into a lightproof container. Store in the fridge.
Coating
The emulsion seems pretty robust and can be melted and cooled numerous times with no real impact apart from a slight speed increase. Coating needs to be carried out in safelight conditions.
To melt the emulsion warm it to 40°c. I use a soft brush to coat, spreading the emulsion out quickly and then finishing by going over the surface slowly and gently with the brush to remove any air bubbles. Paper wise I've never had any problems with this emulsion, as long as the paper can stand up to being processed it should be fine. I find Saunders Waterford works best for me. Peg the paper up to dry in complete darkness then store it in a lighttight bag.
The coated paper keeps well. Contact print it under a bare bulb - I use a 150w tungsten bulb at a distance of a metre or so and get exposure times around 20 seconds. Processing is in normal black and white chemicals, just being careful with the paper surface which will be delicate when wet.