4

I'm considering a range of possible desiccants for equipment & component anti-humidity storage.

The most commonly used is probably Silica gel.
Products using Calcium Chloride are commonly used for general dehumidification.
Molecular sieve materials (eg zeolites) offer 'gold standard' desiccation performance, but also usually high prices.

Obviously (hopefully) applying Calcium Chloride to camera or other surfaces is an invitation to disaster. I'm wondering if using CaCl2 in a sensible manner as described in the question below may still have adverse effects. I'd expect not, but I would rather not find out otherwise "the hard way".

Question:

  • If I use Calcium Chloride in a mechanically stable container at the bottom of a dry space, use a separator to trap any dust and a container to trap any fluid which leaves the desiccant, is it liable to be safe for moisture removal purposes.

  • How does this compare safety wise with other chemical desiccators?

Answers based on experience, and opinions based on well founded theory are most welcome

Some results of various searches:

SE:

How do I prevent condensation in my waterproof GoPro casing?

Nikon D4 possible water damage

What could cause exposure problems after my camera got wet?

How effective is a desiccator box?

Other:

Web search - Calcium Chloride vapor pressure

Basic Equations for Properties of Common Liquid Desiccants

Added:

I've acquired 1 kg of indicating silica gel. I'll use that for my immediate needs and carry out some experiments with that and calcium chloride longer term to compare efficacy and real world 'unwanted' effects.

Philip Kendall
  • 21,867
  • 6
  • 67
  • 101
Russell McMahon
  • 19,630
  • 1
  • 44
  • 79
  • With respect to a number of now deleted comments and flags: it is fine that community members disagree on whether something is on topic. I believe everyone involved was acting in good faith, but nuance is easily lost over text so please all be deliberately gentle with your phrasing. Discussion specifically about this question can continue here, but please take any more general discussion to meta or chat as appropriate. Thanks all. – Philip Kendall Aug 18 '23 at 16:21

1 Answers1

7

I would avoid calcium chloride as a desiccant around metal/mechanical and electronic devices. Calcium chloride is a great desiccant, don't get me wrong -- a little too good for this application. It will continue to draw water from the air until it dissolves itself (deliquesces), which can cause the solution to overflow a container that was too full when the CaCl2 was dry. Even if the container doesn't overflow, it may be subject to spills if the camera storage cabinet or bag is moved.

I'd recommend silica gel, either packets or loose inside a ventilated container with small enough mesh to retain the beads). This material won't take up as much humidity as calcium chloride, but is chemically pretty inert, won't deliquesce, and can be "recharged" by dry heating (a home oven works fine). There's a good reason almost all commercial dessicants that go inside packaging are filled with silica gel.

Zeiss Ikon
  • 7,141
  • 13
  • 37
  • I'd need to name myself "Box Brownie" if I followed your naming system :-) . || I carefull stipulated location and containment of the CaCl2. Coat a lens (or LED in my immediate application) with it and I'd expect disaster. I'm wondering if there are any "atmospheric" effects or whatever. || Upvoted. – Russell McMahon Aug 15 '23 at 11:41
  • 1
    @RussellMcMahon Once the CaCl2 deliquesces, you can get the salt carried in to the air with evaporation (just as with sea water, even when dead calm). Not much, but it doesn't take much to corrode solder joints and battery contacts... – Zeiss Ikon Aug 15 '23 at 12:42
  • 1
    @ZeissIkon You don't even need the calcium chloride to evaporate. Just chlorine gas venting off the wet mixture can cause any metal it touches via air contact to corrode. – Michael C Aug 17 '23 at 15:49