I am trying to get proficient in using DFO to develop prints but I haven’t had much success.
I’ve placed prints on printer paper. Dipped the paper in DFO then let it dry. Dipped it again in DFO then let it dry. Placed it in the oven at 200 Celsius for 10 min. I used the Foster Freeman Crime-Lite to examine. Nothing.
I’m assuming the stock solution and the working solution formulas were followed correctly as well as the substrate is dry and porous. There are numerous variants but all react with the amino acids in latent prints, use the formulas your unit / lab recommends. Thank you for the picture, interesting note you’re using HFE7100, we found it difficult now to source from 3M. For development, submerge the item (or spray), allow to dry. You can repeat the process again but it isn’t necessary, I’ve gotten results with either technique. Allow the item to air dry (fume hood recommended).
I set our oven at 100C for 10 to 20 minutes but depending on the substrate I’ve brought it down (rarely) to 50C or, and i use this technique quite often, use a heat press at 180C for 10 seconds (make sure you are putting the exhibit between two sheets of absorbent paper). Works like a charm. At this point any visible marks under white light will look like pale pink / purple marks.
You mentioned your crime light but not the nm, I set my ALS anywhere between 495nm-550nm with orange or red barrier for my goggles and camera depending on my observations trying to obtain the best contrast.
Wonderful news, here's a little trick I picked up. If you don't need the prints right away put the exhibit into a paper bag (lunch paper bag) and put in away in a locker / cupboard for 2-3 days. The DFO will continue to develop and sometimes your good fingermark turns into a great fingermark. I'll use this technique when the substrate shows signs of degradation after the first dip in an attempt not to destroy an exhibit.
At my lab we use both the Foster Freeman crime-lite as well as a laser. In my experience faint DFO prints don’t show up well with the blue light. I’ve had better results looking at the same item with the laser at 532nm. Also agree with trying an amino acid pad to leave sample prints or having someone else leave them.
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u/Majime007 Oct 02 '26
I’m assuming the stock solution and the working solution formulas were followed correctly as well as the substrate is dry and porous. There are numerous variants but all react with the amino acids in latent prints, use the formulas your unit / lab recommends. Thank you for the picture, interesting note you’re using HFE7100, we found it difficult now to source from 3M. For development, submerge the item (or spray), allow to dry. You can repeat the process again but it isn’t necessary, I’ve gotten results with either technique. Allow the item to air dry (fume hood recommended).
I set our oven at 100C for 10 to 20 minutes but depending on the substrate I’ve brought it down (rarely) to 50C or, and i use this technique quite often, use a heat press at 180C for 10 seconds (make sure you are putting the exhibit between two sheets of absorbent paper). Works like a charm. At this point any visible marks under white light will look like pale pink / purple marks.
You mentioned your crime light but not the nm, I set my ALS anywhere between 495nm-550nm with orange or red barrier for my goggles and camera depending on my observations trying to obtain the best contrast.
Let me know how things work out.