CLPEX Chat Board

Quick question for the board. While looking at our SOP's and seeing which ones we need to update, we noticed in our Indanedione SOP and Processing thermal paper SOP it says that the processor should wait 24-72 hours before examining the evidence if an oven or heat press isn't used (obviously we don't use these on thermal paper). Is there research out there that shows that 24-72 hours is a good waiting period before examining the evidence?

Also, in our Indanedione SOP it says that you can use a humidity chamber, with heat and humidity to develop the evidence. I was always trained on just heat. Anyone else have SOP's written like this?

Indandione prefers dry heat - you can use a heat press or just a plain old iron on a low cotton heat setting.
The recommendation, according to The Fingerprint Detection & Enhancement Manual (Australian Federal Police), is a dry heat press at 160 degrees Celsius for 10 seconds.

You could obviously use a humidity chamber as it has the heat element - but the research shows that the best results are obtained with dry heat. However, indanedione is also dependent on relative humidity - so if you are processing in a particularly dry area, the humidity chamber could be useful to at least get you some humidity, as that is important.

Also, you should be using the formulation which has zinc chloride in it - the indanedione-zinc (IND-Zn) has been shown to be much more effective.

According to The Fingerprint Detection & Enhancement Manual (Australian Federal Police), a modified IND-Zn working solution (without acetic acid) can be used on thermal paper, and they recommend that exhibits are left for at least 24 hours at room temperature for the reaction to proceed. Obviously if you see something develop right away, there is nothing stopping you capturing that immediately. In my experience, I've seen almost all developed prints show up right away, and very rarely seen more prints develop after 24 hours.

Hope this helps.

Bringing this post back up to ask another question. After processing thermal paper with Indanedione we will follow it up processing with Thermanin. Does anyone use something different than Thermanin that may work better? I have had mixed results with it.

Thank you!

Back in the 90's we used another carrier in the ninhydrin formula. Vertrel XF was used as a replacement for HFE. (Which was becoming harder to get at the time)
The surprising thing about the Vertrel XF based ninhydrin was that it was thermal paper friendly (Didn't turn the paper black) and didn't cause inks to run.
I don't know if anyone is using it currently but we had great results with it back then.

Shane

Shane Turnidge wrote: ↑Fri Nov 22, 2019 4:12 am Back in the 90's we used another carrier in the ninhydrin formula. Vertrel XF was used as a replacement for HFE. (Which was becoming harder to get at the time)
The surprising thing about the Vertrel XF based ninhydrin was that it was thermal paper friendly (Didn't turn the paper black) and didn't cause inks to run.
I don't know if anyone is using it currently but we had great results with it back then.

Shane

I have never heard of this before. A quick google search has most pages stating "Call for quote". Grainger has a list price of $589/gallon. That's considerably more expensive than HFE-7100 and that's not cheap to start with. At that cost we would likely stick to Hexane. It wouldn't even be worth the time it would take to validate it for use here. If the price was more reasonable it might be a game-changer based on performance.

I'm pretty sure my former EPU unit used petroleum ether as a base for Ninhydrin. We had HFE7100 also. I referred to them as box wine/well or top shelf formulas

We can mix NIN using acetone, petroleum ether, hexane or heptane. I'll have to go back to the books to better understand the pros and cons of each one, but our preferred flavor is hexane because it doesn't destroy inks. In my experience, the acetone formula tends to work better on brown cardboard. Not sure about the other two. Our main driver for carrier selection is cost. We image thermal paper to preserve it prior to processing then dip and agitate it in the NIN until the black dissolves away. Not the most ideal approach, but we don't get a whole lot of it anyway.

We use the HFE base NIN, but Thermanin for thermal paper. It appears that people are either getting rid of the ink off of the paper or just using Thermanin. Sounds good. I was just trying to find other viable options other than ThermaNin.

Thank you!!

The Vertrel XF was not cheap but we lived in different times.
Our office was faced with the abolition of HFE due to ozone layer concerns in Canada and we had another significant issue. Our office was on the 6th floor of a building which made using flammable chemistry difficult. The police services board had their offices on the 7th floor and they were not particularly fond of the "bucket chemistry" taking place on the floor below.
We tried a number of different chemicals and found most of them obliterated the substrate and were either poor or mediocre with print development.
For reasons I do not understand the Vertrel XF was amazing. We used it for a period of about two years before we were permitted to go back to HFE.

Shane Turnidge