What do I need to create water with negatively charged ions?

Hi, I'd like to do some photography using completely clear ice, as well as to photograph the unique seam pattern that shows up when the ice starts to warm and melt.

I know I need to send an electrical current through a metal plate at the bottom of the water that I'm freezing, but I don't know how much current I need, or how to set it up so it makes the ions negatively charged.

I know, electricity and water.... yay!

Thanks!

Darkmatterx76 wrote:

Hi, I'd like to do some photography using completely clear ice, as well as to photograph the unique seam pattern that shows up when the ice starts to warm and melt.

I know I need to send an electrical current through a metal plate at the bottom of the water that I'm freezing, but I don't know how much current I need, or how to set it up so it makes the ions negatively charged.

I know, electricity and water.... yay!

Thanks!

Water always contains negative ions. Without any applied fields or contaminants pure water will self dissociate to give traces of H+ & OH- ions. (At pH7 these will be equal in concentrations). Impurities in your water will usually increase the number of ions available (salt does this very readily) but I'm not sure if this will help - dissolved salt certainly reduces the freezing point of water.

Any current at all (even just microamps) will cause the ions to move, it is the movement of ions that gives rise to current. The negative ion swill move towards the positive electrode, how much current will be needed for your desired outcome I haven't a clue as I've never heard of using electrical fields to keep ice clear.

I've always heard to get clear ice you must cool it slowly.

Darkmatterx76 wrote:

Thanks for the reply.

The electricity also does something else. It arranges the molecules in a very structured way. As the ice later warms and starts to melt, geometric seams form in the ice that seem to glow due to how light interacts with the seams.

The other issue. Safely adding electricity to metal in water. I'm also not entirely sure yet how to make sure that the charge makes the ions negatively charged.

The key trick that I'm aware of is using water that has few impurities (especially not calcium -- that makes ice cubes with a dull white coat on them!) and removing the air bubbles in the water before freezing. I think slow freezing does that, but boiling the water first is a trick I've heard many times.

I also know that freezing cells while exposing them to microwaves tends to cause less damage to the cells because the ice crystals don't form in a way that breaks the cell walls. Basically, that problem has to do with the fact that water initially expands when it freezes, thus formation of large crystals causes locally large expansions that can rupture cell walls. Perhaps passing an electrical current has a similar effect -- disruption or promotion of crystaline nucleation sites? Not my field.... 

Darkmatterx76 wrote:

The electricity aligns all the molecules in a very ordered pattern which is what causes the geometric seam pattern when it starts to melt. As for why it prevents bubbles, I'm not entirely sure, but my guess is that it excites the molecules enough to release any air dissolved in the water.

I think it causes slow transport of the crystaline nucleation sites... not much different from using microwaves? I do know that + vs - ions can cause directional freezing with impurities pushed to one side. Also, anything that slows freezing tends to make clearer ice because air bubbles have longer to escape.

Interestingly enough, water is actually a terrible conductor of electricity. Electrical current jumps through water piggybacking on the various mineral impurities in the water, not the water itself. For that reason, using distilled water might actually work against you if you try to make the water have a negative charge with electricity. The current might not be able to go through the water properly if there's a lack of minerals.

That's correct. Really pure water generally has high resistance. However, electrolysis of salted water can separate water into Hydrogen and Oxygen even using something as wimpy as a 9V battery .

Where's an electrical engineer when I need one!? :/

Well, I'm a Professor in Electrical and Computer Engineering... but that doesn't help me much with this (I'm really a computer engineer). Maybe somebody involved in battery chemistry?

Darkmatterx76 wrote:

The electricity aligns all the molecules in a very ordered pattern which is what causes the geometric seam pattern when it starts to melt. As for why it prevents bubbles, I'm not entirely sure, but my guess is that it excites the molecules enough to release any air dissolved in the water.

Interestingly enough, water is actually a terrible conductor of electricity. Electrical current jumps through water piggybacking on the various mineral impurities in the water, not the water itself. For that reason, using distilled water might actually work against you if you try to make the water have a negative charge with electricity. The current might not be able to go through the water properly if there's a lack of minerals.

Where's an electrical engineer when I need one!? :/

Normal ice has a well defined structure with the hydrogens on one molecule bonding to oxygens on other molecules in a regular way, the structure is more spaced out that in liquid water which is why ice floats. I'm sure I've got a material science book somewhere with the structure illustrated.

At extreme pressure/temperature there are other forms of ice structures - I think at least 5 of them. These will be well outside the realms of our experience but it's possible an electric field promotes one of them so it's taken instead of the more normal form.

I'd class pure water as a poor conductor rather than a terrible one. Ultra pure water has a resistance of 18 megaohms per cm while many insulators are far above that. FWIW Current flow is not actually necessary to align the molecules an electric field is sufficient.

Darkmatterx76 wrote:

ProfHankD wrote:

I think it causes slow transport of the crystaline nucleation sites... not much different from using microwaves? I do know that + vs - ions can cause directional freezing with impurities pushed to one side. Also, anything that slows freezing tends to make clearer ice because air bubbles have longer to escape.

That's correct. Really pure water generally has high resistance. However, electrolysis of salted water can separate water into Hydrogen and Oxygen even using something as wimpy as a 9V battery .

Well, I'm a Professor in Electrical and Computer Engineering... but that doesn't help me much with this (I'm really a computer engineer). Maybe somebody involved in battery chemistry?

I guess I should have looked at your name a little more closely.

I did try this with a 9V, but it didn't seem to do anything. Part of my issue is not wanting to use to much current, for obvious reasons. I guess I also have to investigate how to make sure that the charge/field is turning the ions to a negative charge over a positive one.

Any applied voltage will create equal numbers of positive & negative ions, with the ions split into different locations by the voltage.

Thanks for your input!

petrochemist wrote:

Normal ice has a well defined structure with the hydrogens on one molecule bonding to oxygens on other molecules in a regular way, the structure is more spaced out that in liquid water which is why ice floats. I'm sure I've got a material science book somewhere with the structure illustrated.

At extreme pressure/temperature there are other forms of ice structures - I think at least 5 of them. These will be well outside the realms of our experience but it's possible an electric field promotes one of them so it's taken instead of the more normal form.

I'd class pure water as a poor conductor rather than a terrible one. Ultra pure water has a resistance of 18 megaohms per cm while many insulators are far above that. FWIW Current flow is not actually necessary to align the molecules an electric field is sufficient.

Thanks for the info.

How would I generate a strong enough EM field in or around a small body of water in a freezer that would force the ions to be negatively charged?

ProfHankD wrote:

Darkmatterx76 wrote:

Thanks for the reply.

The electricity also does something else. It arranges the molecules in a very structured way. As the ice later warms and starts to melt, geometric seams form in the ice that seem to glow due to how light interacts with the seams.

The other issue. Safely adding electricity to metal in water. I'm also not entirely sure yet how to make sure that the charge makes the ions negatively charged.

The key trick that I'm aware of is using water that has few impurities (especially not calcium -- that makes ice cubes with a dull white coat on them!) and removing the air bubbles in the water before freezing. I think slow freezing does that, but boiling the water first is a trick I've heard many times.

Boiling will definitely degas the water, and will remove some amount of calcium since calcium's solubility actually decreases with increasing temperature (which is why hard water is such a huge problem for boilers and hot water heaters...)

Obviously distilled water, with a quick boil to degas just before freezing, is ideal.

I also know that freezing cells while exposing them to microwaves tends to cause less damage to the cells because the ice crystals don't form in a way that breaks the cell walls. Basically, that problem has to do with the fact that water initially expands when it freezes, thus formation of large crystals causes locally large expansions that can rupture cell walls. Perhaps passing an electrical current has a similar effect -- disruption or promotion of crystaline nucleation sites? Not my field....

That's an interesting one.  I do know that microwave absorption changes depending on state - glass becomes vastly more absorptive when hot (which can lead to some fun "stupid microwave tricks" where a glass bottle that normally doesn't react at all to a microwave will melt itself to slag if you just heat up a small portion cherry red before putting it in the oven), and similarly, when water freezes, its molecules lock together in such a way as to no longer resonate at typical microwave oven frequencies, and thus not absorb nearly as much energy.  I am guessing that the microwave behavior here leads to a melt/refreeze cycle at the boundary that behaves similarly to an extremely rapid freeze.

Entropy512 wrote:

ProfHankD wrote:

I also know that freezing cells while exposing them to microwaves tends to cause less damage to the cells because the ice crystals don't form in a way that breaks the cell walls. Basically, that problem has to do with the fact that water initially expands when it freezes, thus formation of large crystals causes locally large expansions that can rupture cell walls. Perhaps passing an electrical current has a similar effect -- disruption or promotion of crystaline nucleation sites? Not my field....

That's an interesting one. I do know that microwave absorption changes depending on state - glass becomes vastly more absorptive when hot (which can lead to some fun "stupid microwave tricks" where a glass bottle that normally doesn't react at all to a microwave will melt itself to slag if you just heat up a small portion cherry red before putting it in the oven), and similarly, when water freezes, its molecules lock together in such a way as to no longer resonate at typical microwave oven frequencies, and thus not absorb nearly as much energy. I am guessing that the microwave behavior here leads to a melt/refreeze cycle at the boundary that behaves similarly to an extremely rapid freeze.

My understanding is that it limits the size of the crystals grown... i.e., prevents large crystaline spread. Don't know the mechanism, just that somebody in my university got a pile of research funding for it. 

"freezing cells while exposing them to microwaves". That's intriguing! What is the source of microwaves?

MacM545 wrote:

"freezing cells while exposing them to microwaves". That's intriguing! What is the source of microwaves?

A magnetron of some type. The work I'm aware of was research a couple of decades ago, so it was probably some strange experimental set-up. I think the set-up was disturbingly close to being a more-carefully-controlled microwave oven inside a freezer. However, let me repeat that this is NOT my field of expertise, and I haven't heard anything about this work in years -- so don't put too much faith in my memories about details of how this works. Unfortunately, I don't have any references handy.