Comment by nvader 2 days ago
I didn't find this in the article, so:
You can "recharge" silical gel by baking in the oven at 120 C for a couple of hours. If you do, be careful to remove the casing before you do, unless it is heat safe.
I have a small collection of oven safe dessicant packs that I keep on hand for emergency drying electronics.
One time I tried drying a water-soaked smartphone in alcohol, but the alcohol got under the LCD screen and made it look blotchy permanently. The phone still worked but I stopped using it.
Yeah, I've had the same issue; as far as I can tell it's not actually the LCD itself but the backlight and the diffuser that end up getting screwed up. If you're trying to save electronics, keep the isopropanol away from the screen.
"You are better off soaking the wet electronics in isopropyl alcohol."
Where I am ethanol (EtOH-95%, H2O-5%) is much cheaper and much more readily available and works almost as well. If silica gel is not available, then a fan works well followed by a warm (not hot) oven baking. Make sure the alcohol has essentially all evaporated first.
Keep in mind that some components can be affected by both EtOH and propan-2-ol — component markings, coil doping resins can dissolve, etc. Both alcohols are also good at removing solder flux resins/residues. (Oh for the days when freon and freon mixtures were available, component damage never happened.)
Devices with power transformers pose special problems, best to dry with alcohol first (hoping enamel coatings on wire aren't softened), then bake in oven on warm heat for a long while, sometimes 24 hours or more is necessary. With transformers it's important that this is done as soon as possible after wetting.
Edit: as I'm reminded by nyanpasu64 keep both alcohols away from LCD screens (likely all screens). I had a netbook PC and put it in a carry bag with a bottle of EtOH and it leaked. The PC still worked but the screen suffered the same outcome.
That may be country specific, but at least where I live, ethanol is much more expensive than isopropyl alcohol (30€/l vs 10€/l) - mostly because of dues on ethanol.
Right, if you live where duty is applied to ethanol then it's expensive. In Australia, where I am ethanol is available as a denatured product. That is, it includes a very small amount (much less than 1%) of denatonium (aka Bitrex) which renders it undrinkable (it's the bitterest substance known). As such, excise tax is not levied.
Here, one liter bottles of denatured ethanol are available in every supermarket everywhere, and up to 20 liters available in hardware stores (at bulk rates it's even cheaper).
For comparison, here denatured ethanol costs about $5/l [in US dollars] versus isopropyl at between $25 and $30/l.
At my work any electronics that have had a water bath or flux-added rework will get an ultrasonic alcohol bath and then a forced air drying run. Alcohol is just so damned good for so much.
I'd be very scared of IPA in an ultrasonic cleaner. Sounds like a recipe for a fire. Or is your machine perhaps designed for safe IPA cleaning?
A few companies do make ultrasonic cleaners that are designed for flammable solvents, but they aren't common.
The easiest option is to just fill a plastic food bag with solvent, throw your part in, seal it with a clip and float it in your ultrasonic bath. The bag contains the vapour for safety, and it's easy to switch between different solvents and solutions.
The machine doesn't get hotter than 50C. IPA isnt igniting at that temp.
99%. 70% if I'm doing parts disinfection for medical devices.
You can just microwave them too, on low power. It's much, much faster and power efficient.
I do microwave. It's pretty easy to not burn, just undershoot it - 10 seconds, see how hot it is, another 10 seconds. Once it's blazing hot shake it back and forth to get the steam off. If it's the colored kind (white when good, pink/blue when full of water) it's easy to tell when it's good. Takes about 30 seconds all together - I recharge my dessicant packs before every use. Of course, people are welcome to spend hours doing the oven method if they want. I just don't personally see an advantage, unless you have an industrial amount of packs to recharge.
is there any harm in overheating silica when drying it out?
Pure silica? It's really just SiO2. It might kind of fragment/ burst if it has a lot of water absorbed and you heat it too fast. Then everything in the vicinity would get sprinkled with fine dust which you shouldn't inhale in large quantities, as it might cause silicosis.
Practical details about the types of desiccant beads and how to dry them.
Cobalt chloride decomposes only at extremely high temperatures and it melts only at very high temperatures (726 °C), which could not be reached, in any case not before all water in the silica gel would be converted to steam and it would be eliminated. Even when no water is left, it is unlikely that the beads with cobalt chloride could absorb enough microwave energy to be heated at very high temperatures.
So by itself cobalt chloride could not cause any problem.
However, I have no idea whether the cobalt chloride is not mixed with some organic binder, to make it stick to the silica gel beads, which could burn in the oven, though that is also unlikely to happen before all water is removed from the gel, allowing an increase in temperature above the boiling temperature of water.
By using low microwave power and short time, so that no boiling of the contained water should be seen, it should be possible to dry even beads with cobalt chloride.
Are there studies on whether it sheds dust and under what conditions?
Also, where are people even still getting cobalt chloride gel? Do they still make it? I sure wouldn't buy any.
I wouldn't even buy the orange to green stuff by choice these days for anything DIY, it's still too toxic when mechanical hygrometers are cheap.
There's silica gel you can buy without cobalt chloride that I use for storing my 3d print filament.
The indicator is supposed to be toxic though. I’ve always seen warnings to never reuse that kind.
If the indicator is cobalt chloride, which is blue when dry and pale pink (possibly almost invisible) when wet, that can be toxic or carcinogenic when ingested in great quantities, or when you inspire a lot of dust of it, but it is not dangerous to handle when in compact form.
It is certainly not something like a poison, where small quantities can have harmful effects, at least not for most people.
Like nickel, cobalt can cause allergies in some people, in which case repeated exposure can have serious effects even in small quantities, in those humans who are sensitive to it.
They can also be died at much lower temperatures, it just takes a lot longer. I dry mine by leaving them on top of a computer at ~35C for a week, I believe the air flow from the fans is important.
The color indicating ones are useful so you can see when they are dry.
At what ambient humidity do you do this? Where I am we are having a dry day at 45% humidity today. Tomorrow it'll be over 90%, and it'll stay between 50% and 90% through the weekend. I would expect that you need a more consistently dry environment for this to work
This sounds like a great idea, but how do you keep it from being "drained" or hydrated?
Immediately take them out of the oven and store in the smallest airtight container you have. Obviously they'll absorb the humidity in the container and whatever is introduced anytime you open it. Ideally, keep them in containers that have an excellent seal and minimal internal volume like quality ESD bags.
If they're not getting hydrated slowly, they're not serving any purpose. The whole point is that water goes into them instead of whatever you're trying to keep dry.
other people are suggesting the microwave rather than the oven. to my mind it seems very possible that you don't keep them from hydrating, you just dehydrate them on-demand.
When my last phone took an unsanctioned swim, my research suggested that a food dehydrator is a last resort. It risks forcing water vapour further into the electronics of the system, rather than encouraging it to move out.
I did find a clever solution online that tried to induce mechanical suction on your phone to force the vapour out, but it was too expensive for a one off use.
In the end I had to resort to the food dryer anyway, after the silica gel failed to work.
You are better off soaking the wet electronics in isopropyl alcohol then trying to dry them in a bag full of desiccant.
One of the things that kills wet electronics is the dried residue that is left behind, creating shorts. Alcohol will wash away the water and leave no residue after it dries.
If the device has ink or glue you'd like to try to preserve, deionized water will mostly work too.