Hey folks. I am not a forensic examiner, but work as a criminal investigator for a small sheriff's department. I try fume (via cyanoacrylate) before sending items to the state crime lab. For years I have used a fish tank, coffee cup heater, cup of hot water, and loctite superglue with pretty decent results.
I have now built a large chamber from a refrigerator, complete with 110 outlets, exhaust fan, internal fan, and front observation window (no more breathing fumes in my office).
My question is about humidity levels. What is optimum, and should I go to the expense of a humidifyer and/or should I just use the "cup o' hot water" and a humidity reader? I don't have much money to spend.
Any suggestions would be appreciated.
Question on Cyano fuming
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Graham F
- Posts: 66
- Joined: Mon Mar 27, 2006 8:53 am
Humidity & CA
Doug
Over the last 20 years or so there have been many references to the use of humidity in the development of latents by cyanoacrylate.
Irrespective of what humidity you utilize it should be remembered that optimum development will occur when the humidity is raised prior to the heat acceleration of the CA.
That said, 75% humidity is generally considered my many to be optimum. Some examiners may differ and wish to use a slightly lower or higher % and there is published literature on this. Indeed, I have often used a higher percentage when the item being processed has been heavily contaminated.
Whilst many examiners have to use an uncontrolled environment such as a fish tank, or similar, they will still get results, but in low ambient humidity environments the jar of water can be only mildly effective. However, this does present the question of how many latents are being lost, by not utilizing a controlled process that is not effectively robust and repeatable.
If there is any way that you can adapt your new system to adjust the humidity to a set level and maintain it at that level, then heat the CA, I am certain your results will be even better than what you have experienced in the past. Additionally, the results will be consistent. Obviously cost will be a driving factor as it is for many labs, but some low cost DIY is always better than nothing at all and if you are using a manual humidity probe inside the tank, remove it prior to glue acceleration.
Regards,
Over the last 20 years or so there have been many references to the use of humidity in the development of latents by cyanoacrylate.
Irrespective of what humidity you utilize it should be remembered that optimum development will occur when the humidity is raised prior to the heat acceleration of the CA.
That said, 75% humidity is generally considered my many to be optimum. Some examiners may differ and wish to use a slightly lower or higher % and there is published literature on this. Indeed, I have often used a higher percentage when the item being processed has been heavily contaminated.
Whilst many examiners have to use an uncontrolled environment such as a fish tank, or similar, they will still get results, but in low ambient humidity environments the jar of water can be only mildly effective. However, this does present the question of how many latents are being lost, by not utilizing a controlled process that is not effectively robust and repeatable.
If there is any way that you can adapt your new system to adjust the humidity to a set level and maintain it at that level, then heat the CA, I am certain your results will be even better than what you have experienced in the past. Additionally, the results will be consistent. Obviously cost will be a driving factor as it is for many labs, but some low cost DIY is always better than nothing at all and if you are using a manual humidity probe inside the tank, remove it prior to glue acceleration.
Regards,
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Pat A. Wertheim
- Posts: 872
- Joined: Thu Jul 07, 2005 6:48 am
- Location: Fort Worth, Texas
For decades I used a homemade cabinet. In trying to humidify the thing prior to fuming the superglue, I found that the surface area of the water was the key. The greater the surface area, the better it would humidify the cabinet. I ended up using a stainless steel developing tray, but I'm sure a pyrex casserole dish or 10" X 14" cake dish would do great. I just used the hottest tap water available in the dish and it worked beautifully. Best of luck!
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Neville
- Posts: 307
- Joined: Mon Jan 23, 2006 11:44 am
- Location: NEW ZEALAND
humidifying
I have never had the privilege of visiting Tennessee but my perception is one of a humid climate, do you actually need to worry about a humidifier.
In Auckland NZ, we have successfully been fuming with supper glue without a humidifier for over 20yrs. We did some initial experiments which indicated that our results were not improved by humidifying.
We are located on a thin area of land surrounded by oceans so we get enough humidity for 90% of the year. Check your humidity readings locally if it’s over about 60% I don't see that it's an issue.
In Auckland NZ, we have successfully been fuming with supper glue without a humidifier for over 20yrs. We did some initial experiments which indicated that our results were not improved by humidifying.
We are located on a thin area of land surrounded by oceans so we get enough humidity for 90% of the year. Check your humidity readings locally if it’s over about 60% I don't see that it's an issue.