Homemade Photographic Emulsion DNBP
2-(2,4-dinitrobenzyl)pyridine. The name just trips off the tongue eh? But that’s the name of a chemical I’ve been playing with to make a photographic emulsion.
2-(2,4-dinitrobenzyl)pyridine (which I will now refer to as DNBP) is sensitive to the upper end of the visable spectrum (i.e. violet) as well as ultraviolet. When exposed to these wavelengths the compound turns from a very pale (almost white) yellow to a vivid blue and remains this way for several hours before reverting back to it’s original form. This means that one negative can be reused as many times as you like – all you need to do is capture the image formed digitally before it disappears.
I made my negative by mixing DNBP (I’ll post a method for making DNBP later) with acrylic gel medium then spreading it onto a piece of card around 6×9 cm. This was then loaded into my Moskva II medium format camera. Since it’s only sensitive to the blue and UV end of the spectrum and normal glass lets little UV through exposure times were quite lengthy – on a sunny day around 45 minutes. After some experimenting I’ve found that silhouettes work best (see the last image of the tree) I’m going to try setting up some still life shots with objects that have a distinctive outline. It’ll be a while before I post about it again though – at the moment I only have one Neg which means one shot per day and getting the exposure right can be tricky. I will give me time to write out the method for those of you who are interested in preparing DNBP though (knowledge of chemistry and kit essential)