Absorbent Industries Humidity Indicator Cards Cobalt Free, 6 Dot, Pack of 25,Brown,HIC6DOTCOFREE-25pk

These worked great. I was staying in Hawaii and put these inside things like the box for my sewing machine, along with desiccant packets. I also left one out as a control. The one I left out showed about 90% humidity and the one in with the sewing machine showed about 30% humidity.

Well, this is working, but as others said it is a little difficult to understand how to read them; all the spots turned to a pale green colour, which is "more green" than 10% spot: does anyone know how to read them? in the pictures below, you can see the strips before use and while in use.

The cobalt-free technology humidity indicator spots, which change to various shades of brown/grey, are harder for me to read than the cobalt based humidity indicators that change color from blue to pink.

They work, but not the easiest to read. It doesn't "turn" green, but rather brown to a "brownish green" to green. Kind of of a judgement call how brownish green is too green.

I ordered this Cobalt free package. I received the blue to pink indicator cards with carcinogenic Cobalt.

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Seems to work just as described. Much better alternative to "moisture indicating" silica gel, which may have potential cancerogens and be dangerous if swallowed by kids or pets. Regular silica gel is non-toxic and basically harmless. This piece of paper is as well and this pack comes with plenty to use. Just be sure to seal the ones you're not using (or at least out them in a ziploc so they'll be "fresh" later.