Author Topic: I think it's the hotplate on-off cycles causing residue.  (Read 98 times)

Offline Turbidaceous

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I think it's the hotplate on-off cycles causing residue.
« on: June 06, 2020, 02:37:19 PM »
I have a theory that the reason, despite doing everything right, I sometimes end up with a small amount of sediment which settles or contributes to a little bit of opalescence when shaken up, is due to the hotplate. The hotplate regularly heats up, then turns off... waits... then turns on again etc. So since I have no stirring, only convection currents, my theory is the temporary lack of enough movement is what creates a little bit of silver oxide to precipitate or what ever.

Do all hotplates do this, where they heat up and turn off and only turn on again when they want to continue to heat?

Given this fact of mine, at least, what would be better to use higher heat? Or should I use lower heat in order to help mitigate this issue? I don't always have it, so I am just interested on theories as to what I will try next time I am ready to make a batch.

Offline SaltyCornflakes

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Re: I think it's the hotplate on-off cycles causing residue.
« Reply #1 on: June 13, 2020, 04:17:26 AM »
It's possible that the on-off cycle does not always agitate the water enough. But I would assume the lack of stirring to be the culprit. When you don't stir, you get slower reduction because the agents are less available. Lowering mA to compensate may help there. You can also get 'silver wisps' off the anode or more visible plate-out. I don't think stirring just disperses this, rather it prevents it from forming. I think a lack of motion in the water, especially around the electrodes where reactions happen and things can 'back up', is just bad for Colloidal Silver quality.

Make sure you submerge the anode as much as possible. Try lowering mA. Try an excess of reducer / capping agent. It's especially important with high heat to use more. As an example: You want to make 1 litre of 20ppm and add reducer for exactly 1 litre of 20ppm. While it should be able to convert all, it may not do so fast enough. Higher concentration of reducer in the water = less chance for gunk to collect on the cathode (all gunk on the cathode is wasted silver that throws off your calculation) and so better reduction overall.

Offline Turbidaceous

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Re: I think it's the hotplate on-off cycles causing residue.
« Reply #2 on: June 13, 2020, 12:16:54 PM »
I always make 1L of 100ppm and I add maybe 100ml more of malto as a bit of a buffer because I don't want to risk adding to many non-functional particles and spreading out the silver to where there's less surface contact or something.

I have a decently large anode 3.5x9cm but I went down from 20ma to 15ma. I could go down to 10ma but I am not a fan of the idea of it both taking longer and also using more electricity through heating. Over all the quality I come out with is very decent, very transparent red when you look at a light source through a large container of it. It's just annoying that a little bit of unreduced sits there at the bottom. I might try 10ma next time (not made any in ages).

Offline SaltyCornflakes

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Re: I think it's the hotplate on-off cycles causing residue.
« Reply #3 on: June 13, 2020, 04:17:12 PM »
I use 5mA and even that is pushing it sometimes when I want to do a cold run. Out of all the reducing agents I've tried, Malto has been the slowest.

Also at 100ppm, you should be seeing a dark brownish amber. And when you dilute to 20ppm, you should be seeing a bright yellow. A red color at 100ppm sounds to me like larger particle size. What do you get when you dilute? A picture or two would help, as color descriptions are a bit iffy and colloids like to look different depending on light source etc.

Offline Turbidaceous

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Re: I think it's the hotplate on-off cycles causing residue.
« Reply #4 on: June 13, 2020, 07:58:55 PM »
When I dilute it, it is perfect colour for 20ppm as in all the images shown on the site. But the size of the container it is in, if I hold it up and look outside or at a lightbulb it's a nice red colour. If I drop it on a tissue it's a darkish yellow. So it's good.