CLPEX Chat Board

I am looking into buying a countertop convection/ microwave oven for DFO and Ninhydrin processing vs. paying big bucks for an oven designed specifically for processing. I have found some models where an exact temperature can be set. Any suggestions or caveats on going this route (and no, I won't use it to bake chicken for the next employee potluck)?

What humidity controls does your intended "convection/ microwave oven" have?

DFO processing requires very low humidity, whereas Nin requires high humidity 65% - 75%. Heat on its own is not sufficient for optimal development. Will it work - yes. Will it work well - no.

To carry out the Ninhydrin process effectively a humidified oven providing close control and rapid recovery of temperature and humidity after door opening is required. Uniform temperature and humidity throughout the oven are required…….Manual of Fingerprint Development Techniques PSDB.

If you just require the heat and a lower latent development rate, why pay $000’s for a convection/microwave oven. Save your money and pay $20 for a steam iron, albeit a steam & wool (linen whatever) setting will not equate to 80°c 65% humidity. It will work better, but not as good as a controlled environment chamber. Lower development ratio = lower results.

I've had nice results for both nin and DFO with the Caron oven.

A couple of suggestions:

• Make sure the shelves are large enough for your intended use. At least 9.5" x 12" for letter size paper in the U.S.
• A drip pan that will fit on top of the bottom heating elements can be partially filled with water to provide humidity for ninhydrin development. (Remember to remove the water for DFO development)
• I have used a convection toaster/oven (non-microwave) with good results in the past.

Regards, RLT

Just remember that by using an oven or microwave there is a trade off, speed for more back ground staining. I would still advise putting the treated paper (once Dried) into a sealed plastic bag and leave for a week in a warm spot, Less back ground staining and better contrast, I gave up on ovens years ago.
But I agree if you must go down that track a steam iron is much cheaper.

Ok, so as Emeril would say “let’s turn it up a notch.”

The latent community has always conducted itself in a “cheap” fashion. We have always striven to just “make do” with what we have, or find ways to bastardize the process to save a few $’s. Would this approach be acceptable in other forensic disciplines. Would say DNA use a large paper sack instead of using a PCR enclosure? Would Drug Chemistry keep the GS/MS running with “pink string and sealing wax,” if you get my drift?

Whether they would or would not, in latents we sell ourselves cheap in the belief that saving a few dollars will produce great results. This may produce results, but they may not always be great. People may say “you just want the best [most expensive] stuff. The answer to this is no I do not. I just want the stuff that is robust and will continue to be repeatable and produce the best possible results. If it costs more, so be it.

Do we fully explain to management that the proposed new equipment may well not reveal the prints of the perp in a homicide, or the terrorist making the IED? Do we explain to the court that the evidence could have been better and may have identified more suspects than the current defendant on trial etc?
You can use an oven/microwave and at times it will work, but the question is not that you developed latents, but what latents did you not develop with this mediocre system.

If such mediocrity is not allowed in other disciplines why do we continue to fully embrace it with open arms?

All valid points for sure and I have very little to add save I have never tried to use a conventional oven for NIN or DFO development. As one post mentioned NIN requires high humidity whereas DFO does not. Some questions do come to mind though in using a conventional oven with high humidity. Would a conventional oven be sealed well enough to allow the humidity to attain levels for proper NIN development? I know my oven at home seems to vent excess moisture from the oven... just a thought before going down that road.

To respond to another post about taking the cheap road... I hear what's being said and do agree but I also realize that not every agency has the budget to have the Caron ovens or all the other bells and whistles. So, to that end I have always found a decent steam iron does a pretty darn good job... albeit a little more labor intensive but hey, that's the cost of saving the $$.

garywood702 wrote: ... Some questions do come to mind though in using a conventional oven with high humidity. Would a conventional oven be sealed well enough to allow the humidity to attain levels for proper NIN development? ....

With an electric toaster oven I have been able to achieve 75-80% humidity (as checked with hygrometer) by careful setting of temperature control... approx. 200 deg F - will vary depending on oven. You can even 'tune' to your preferred humidity range.

Have never used a microwave, however throughput can be increased approx. 10X or more by use of a large enough conventional oven. Of course, careful visual monitoring of developement is necessary or you can easily over-develop with increased bacground staining, as previously mentioned.
Regards, RLT