i am curently looking into different methods of using low heat sources to develop latent marks on thermal papers.
if any one has any examples that they have had success with could you please let me know
any other info on the subject would be greatly appreciated
thanks
development of latent marks on thermal receipts
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Liz
- Posts: 1
- Joined: Fri Dec 09, 2005 11:36 am
Development of Latent Prints on Thermal Paper
Our lab recently added the use of ThermaNin to our manual to use whenever we have a case involving thermal paper. I did some testing before it was utilized with real cases and found that if you processed it in a certain order it tended to work better and have better results at each step.
Cyanoacrylate Fume
Iodine
ThermaNin
Low Heat Application (hairdryer)
Magna Powder
By fuming the evidence first the powder seemed to work better. The iodine also worked well on the thermal side of the paper (especially with fresh prints), but tended to display results different from use on regular types of paper. The iodine turned the prints a dark green color and tended to not fade over time so over exposure in the iodine tank was watched carefully. The thermanin worked pretty good on prints that tended to be fresher than ones left over periods of time (1 month, 6 months and 1 year). The use of the hairdryer is very touchy since it is very easy to scorch the paper and there is no way to my knowledge that this can be un-done (there is an article about this process in the JFI). Finally, we use magna powder, which has helped to darken up some already developed prints.
Hope this helps!
Cyanoacrylate Fume
Iodine
ThermaNin
Low Heat Application (hairdryer)
Magna Powder
By fuming the evidence first the powder seemed to work better. The iodine also worked well on the thermal side of the paper (especially with fresh prints), but tended to display results different from use on regular types of paper. The iodine turned the prints a dark green color and tended to not fade over time so over exposure in the iodine tank was watched carefully. The thermanin worked pretty good on prints that tended to be fresher than ones left over periods of time (1 month, 6 months and 1 year). The use of the hairdryer is very touchy since it is very easy to scorch the paper and there is no way to my knowledge that this can be un-done (there is an article about this process in the JFI). Finally, we use magna powder, which has helped to darken up some already developed prints.
Hope this helps!
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Scott Murfitt
- Posts: 1
- Joined: Mon Dec 05, 2005 11:49 am
Thermal Paper
I have been treating thermal paper with what I have seen referred to as dry ninhydrin. I use standard ink blotting paper which is cut to a size slightly larger than the item to be examined. Blotter paper is treated with ninhydrin and allowed to dry. Place the item between two pieces of the treated blotter paper and seal in a ziploc bag for 7-10 days. The prints are sometimes weak but have very good detail. After the first 7-10 days, if no prints have developed I leave it another 7- 10 days as development time is not consistent. I have had very good success with this method. Also there is no damage to the actual thermal paper document as is caused by the usual heating methods. The down side is the length of time involved.
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Tony
- Posts: 1
- Joined: Mon Dec 12, 2005 11:01 am
- Location: London
Thermal receipts
I too have been using low heat sources to develope marks on thermal type papers. I use our Nin humidity chamber with all the humidity turned off. It does require careful watching, but will develop marks
Recently, I've been treating with NIN and as expected the paper turns black. However, by leaving the paper in the NIN for an extended time the black clears to a dull white, maybe a pale gray. Had to agitate for a while and sometimes even refresh the NIN in the tray.
The best results I've obtained is by using Physical Developer though and more often than not these are developed after the previous heat and NIN treatments.
Tony
Recently, I've been treating with NIN and as expected the paper turns black. However, by leaving the paper in the NIN for an extended time the black clears to a dull white, maybe a pale gray. Had to agitate for a while and sometimes even refresh the NIN in the tray.
The best results I've obtained is by using Physical Developer though and more often than not these are developed after the previous heat and NIN treatments.
Tony
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Heidi Fraser
- Posts: 52
- Joined: Tue Jul 05, 2005 11:38 am
- Location: Eugene, Oregon
We use a specialty ninhydrin formula for thermal paper that was published in the JFI by one of our own, Jon Stimac. This method works well without discoloring thermal paper and requires NO application of heat. We leave paper processed with this formula to develop in the dark for 48 hours, rather than the 24 our procedures manual requires for Ninhydrin in pet ether or HFE. This seems to compensate for the lack of a heat and humidity step in development.
I don't know the reference for the artcile right off, but if you're interested, email me privately and I can write Jon and ask him.
Heidi
I don't know the reference for the artcile right off, but if you're interested, email me privately and I can write Jon and ask him.
Heidi
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Hillary Moses
- Posts: 28
- Joined: Mon Jul 11, 2005 11:46 am
- Location: Hayward Police Department
Wow... I experimented with Scott's method, and was very impressed. Beautiful, contrasting, well-defined ridge structure resulted after ten days. I used plain white printer paper with my experiments, and did ten separate receipts. I was skeptical, but I was pleasantly surprised and have already used this method on a case. For departments that have their wallets tightly clenched in iron fists, this method is great.