I signed for the gloves, returned to my office, and spent the next half hour proofing and signing reports. Then I walked back to the corridor occupied by biology, and entered a door marked Incendie et Explosifs. Fire and Explosives.
A man in a lab coat stood in front of an enormous piece of machinery. A label identified it as an X-ray diffractometer. He didn?t speak and I didn?t say anything until he had removed a slide with a small white smear and placed it on a tray. Then he gave me eyes as soft as a Disney fawn, lids drooping, lashes curling back like petals on a daisy.
?
?
I held up two plastic bags.
?Let?s get started.?
He led me into a small room with an apparatus the size of a photocopier, two monitors, and a printer. A periodic chart of the elements hung on the wall above.
Lacroix laid the evidence bags on a counter and pulled on surgical gloves. Gingerly, he withdrew each suspect glove, inspected it, then laid it on its plastic bag. The gloves stretched across his hands looked identical to those on the counter.
?First we look for gross characteristics, details of manufacturing. Weight. Density. Color. How the rims are finished.? He turned each glove over and over, examining as he spoke. ?These two look quite similar. Same rim technique. See??
I looked. The wrist of each glove ended in a border that rolled outward onto itself.
?They?re not all like that??
?No. Some roll in, some roll out. These are both outies. So. Now we see what?s in them.?
He carried Gabby?s glove to the machine, raised the cover, and placed it on a tray inside.
?With very small samples I use those little holders.? He pointed to a tray of small plastic tubes. ?I stretch a square of polypropylene window film across the holder, then use press-on tabs to make a sticky spot to hold the fragment. That?s not necessary with this. We?ll just put the whole glove in.?
Lacroix flipped a switch and the apparatus whirred to life. A box positioned on a pole in one corner lit up, the word X RAY white against a red background. A panel of buttons glowed, indicating the machine?s condition. Red: X rays. White: Power. Orange: Shutter open.
For a few moments Lacroix adjusted dials, then he closed the cover and moved to a chair in front of the monitors.
?
A desert landscape appeared on the first monitor, a granular backdrop of synclines and anticlines, with shadows and boulders scattered here and there. Superimposed on that scene was a series of concentric circles, the two smallest and most central shaped like footballs. Two hashed lines intersected at right angles, forming a cross directly over the bull?s-eye circles.
Lacroix adjusted the image by manipulating a joy stick. Boulders shifted in and out of the circles.
?That?s the glove we?re looking at, magnified eighty times. I?m just picking a target location. Each run samples an area of about three hundred microns, approximately the area inside the dotted circle. So you want to direct your X rays onto the best part of your sample.?
He shifted the crosshairs a few more moments, then settled on a boulderless patch.
?There. That should be good.?
He flipped a switch and the machine hummed.
?Now we?re creating a vacuum. That?ll take a couple of minutes. Then the scan. That?s very quick.?
?And this will determine what?s in the glove.?
?
The humming stopped and a pattern began to form on the right-hand monitor. A series of tiny red mounds sprouted across the bottom of the screen, then grew against a bright blue background, a thin yellow stripe up the middle of each. In the lower left-hand corner was an image of a keyboard, each key marked with the abbreviation for an element.
Lacroix typed in commands, and letters appeared on the screen. Some mounds remained small, others grew into tall peaks, like the giant termite castles I?d seen in Australia.
?
?Zinc. That?s standard. It?s found in all these gloves.?
He indicated a pair of peaks to the far left, one low, the other rising three quarters of the distance up the screen. ?That low one is magnesium. Mg. The tall one marked Si is silicon.? Farther to the right a double peak bore the letter S.
?Sulfur.?
A Ca peak spired halfway up the screen.
?Quite a bit of calcium.?
Beyond the calcium a gap, then a series of low mounds, foothills to the zinc pinnacle. Fe.
?A little iron.?
He leaned back and summarized. ?Pretty common cocktail. Lots of zinc, with silicon and calcium, the other major components. I?ll print these, then let?s test another spot.?
We ran ten tests. All showed the same combination of elements.
?Right, then. The other glove.?
We repeated the procedure with the glove from Tanguay?s kitchen.
The peaks for zinc and sulfur were similar, but this glove contained more calcium, and had no iron, silicon, or magnesium. A small spike indicated the presence of potassium. It was the same on every run.
?What does this mean?? I asked, already certain of the answer.
?Each manufacturer uses a slightly different recipe for the latex. There will even be variation among gloves from the same company, but it will be within limits.
?So these gloves are not a pair??
?They weren?t even made by the same company.?
He got up to remove the glove. My mind was stumbling over our finding.
?Would X-ray diffraction give more information??
?What we?ve done, X-ray microfluorescence, tells what elements are present in an object. X-ray diffraction can describe the actual mixture of the elements. The chemical structure. For example, with microfluorescence we can know that something contains sodium and chloride. With diffraction we can tell that it is made up of sodium- chloride crystals.
?To oversimplify, in the X-ray diffractometer a sample is rotated and hit with X rays. The X rays bounce off the crystals, and their pattern of diffraction indicates the structure of those crystals.
?So one limitation with diffraction is that it can only be done on materials with a crystalline structure. That?s about eighty percent of everything that comes in. Unfortunately, latex is not crystalline in structure. Diffraction probably wouldn?t add much anyway. These gloves are definitely made by different manufacturers.?
?What if they?re just from different boxes? Surely individual batches of latex must vary.?
He was silent for a moment. Then:
?Wait. Let me show you something.?
He disappeared into the main lab and I could hear him talking to the technician. He reappeared with a stack of printouts, each composed of seven or eight sheets showing the familiar spire and steeple patterning. He unfolded each series and we looked at the variations in pattern.
?Each of these shows a sequence of tests done on gloves from a single manufacturer, but sampled from different boxes. There is variation, but the differences are never as great as those in the gloves we just analyzed.?
I examined several series. The size of the peaks varied, but the components showed consistency.
?Now. Look at this.?
