I haven't dealt with Blade-Tech personally, but it took a long time to have a couple questions answered via email. If you use the phone you generally get a lot better luck with that company, whose products are pretty nice in my opinion.
Concealex is a 100% virgin polymer which has similar properties to Kydex, but the chemical structure is different. Here's what I've found from my extensive use with Kydex and somewhat more limited use of Concealex:
1) Concealex feels less "platic" on the outside. The camo patterns almost feel like cardboard on the surface, to me. The texture is a little more muted on Concealex, which also means that slightl overhating (makes the surface shiny) is more obvious. The inner surface is more slick on Concealex than on Kydex.
2) Concealex curls up and really warps a lot when heating while Kydex stays pretty much flat. Concealex also seems to shift more in heating and cooling while Kydex does this to a lesser degree.
3) Kydex molds better. Maybe I have been using the wrong setup for Concealex, but Kydex molds really well at 200-225 degrees to get nice crisp definition, but Concealex sort of takes a general form and doesn't seem to want to hug the knife quite as much as Kydex does.
Perhaps someone from Blade-Tech will spot this and give me some pointers on what I am doing wrong, but despite the pattern limitation of Kydex, I prefer it over Concealex as a material for sheaths.
Oh...one other thing...my belt clips are a good way to judge the stiffness of a material because of the way they are folded, and the Kydex ones are significantly stiffer than the Concealex ones of similar proportions (and same thickness).
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My Custom Kydex Sheath page
http://www.geocities.com/CollegePark/Lab/1298/knifehome.html
Palmer College of Chiropractic
On Two Wheels
