Link to HomeBrowse by Materials
Browse by Craft

Photo Emulsion Exposure

A popular method of making stencils for screen printing is to use the Diazo Photo Emulsion.  The screen is prepared with the photo emulsion and a negative printed on acetate is placed on the screen before it is exposed to a bright light source (find out more about Diazo Photo Emulsion).

Here is a useful excerpt from Ruth Brown's book Digital Imagery on Fabric, page 74.  Ruth's book explores a number of techniques including cyanotypes, Bubble Jet Set 2000 and photo transfers. 

‘You can use various light sources to expose a photoemulsion screen ranging from Photoflood bulbs to a sunbed. Received wisdom is that you use a 250w BBA photoflood bulb suspended above the surface on which you will have a screen. The guideline is that the distance from the light source should be something like the diagonal of the screen, if you want somewhere to start. If you are preparing a big screen and you have the light source too close the edges may not get enough light and won’t expose correctly.

Speedball give a chart of suggested timings for two different bulbs:

150 Watt Bulb, Clear Incandescent

screen size bulb height exposure time
8 x 10 inches 12 inches 45 mins
10 x 14 inches 12 inches 45 mins
12x 18 inches 15 inches 1 hr 14 mins
16 x 20 inches 17 inches 1 hr 32 mins
18 x 20 inches 17 inches 1 hr 32 mins

BBA No. 1 Photoflood (250 Watt)

screen size bulb height exposure time
8 x 10 inches 12 inches 10 mins
10 x 14 inches 12 inches 10 mins
12x 18 inches 15 inches 16 mins
16 x 20 inches 17 inches 20 mins
18 x 20 inches 17 inches 20 mins

Note:

These timings assume you are using a foil pie plate above your bulb to act as a reflector

The photoflood bulb can get pretty hot – probably won’t be able to use it in a normal lamp fitting. Ask where you bought the photoflood bulb from what they would recommend.’

Please note that once the emulsion is mixed with the sensitiser it should be applied and exposed within a few days. The mix will cure over time at room temperature, even if kept in the dark, and this will be complete within a few weeks.
 

Follow our pages on:
visit Facebook.comvisit Twitter.comsee our Blog