Photo Lubricants Drying Out In Low Relative Humidity Storage.

[Lemmythink]

It seems fungus can be an inevitable thing the older a lens gets. I live in a damp house and try to regulate it with the help of Relative Humidity (RH) Meters. They indicate I can drop the humidity in a container with silica gel beads to their limit of detection at 10% very easily and quickly. This seems a brilliant way of getting the internals of gear dry, because if only a little gas exchange occurs in and out of the lens, the very dry air will have a big effect. So why don't we all do this as a matter of fact being so easy and devastating to fungus? I did see one person mention a RH% of less than 35% would dry out the lubricants used in photo equipment. Is this the case? I would think if they are not water based then a dry atmosphere would not affect them?

 

[Sirius Glass]

It seems fungus can be an inevitable thing the older a lens gets. I live in a damp house and try to regulate it with the help of Relative Humidity (RH) Meters. They indicate I can drop the humidity in a container with silica gel beads to their limit of detection at 10% very easily and quickly. This seems a brilliant way of getting the internals of gear dry, because if only a little gas exchange occurs in and out of the lens, the very dry air will have a big effect. So why don't we all do this as a matter of fact being so easy and devastating to fungus? I did see one person mention a RH% of less than 35% would dry out the lubricants used in photo equipment. Is this the case? I would think if they are not water based then a dry atmosphere would not affect them?

In your climate I would be very careful about using leather cases to store cameras and lenses due the humidity helping fungus grow.

 

[loccdor]

I once put my cameras away in a cardboard box for ten years. I didn't open it. Mold grew on the leather cases, in agreement with Sirius' statement. It didn't grow on anything else. Humidity in this house is around 60% in the warm half of the year and 30% in the cold half due to a forced air heating system.

 

[4season]

I don't think extremely low humidity would cause problems with lubricants, but natural materials such as leather, paper and wood may be another matter. I think a compromise like 50% RH @ 25C would do nicely.

 

[RalphLambrecht]

I don't think extremely low humidity would cause problems with lubricants, but natural materials such as leather, paper and wood may be another matter. I think a compromise like 50% RH @ 25C would do nicely.

I control the RH in my photo storage room to be between 35 and 50% with the help of a dehumidifier. So far, so good.

 

[Harry Callahan]

...
I did see one person mention a RH% of less than 35% would dry out the lubricants used in photo equipment. Is this the case? I would think if they are not water based then a dry atmosphere would not affect them?

I definitely am not an expert on this, but i know that oil can evaporate. It takes a lot longer than water, but it does.
Thinking of physical class in school, a liquid only can evaporate if the air is warm enough - and not saturated. If RH is like 90%, water in a bowl won`t evaporate any more because air is (nearly) saturated.
Then it may be hard for this air to still take up evaporating oil.
If the air is low RH it should be able to take up more oil evaporation - so it very well could be that too dry air may increase drying of lubricants.

 

[RalphLambrecht]

I definitely am not an expert on this, but i know that oil can evaporate. It takes a lot longer than water, but it does.
Thinking of physical class in school, a liquid only can evaporate if the air is warm enough - and not saturated. If RH is like 90%, water in a bowl won`t evaporate any more because air is (nearly) saturated.
Then it may be hard for this air to still take up evaporating oil.
If the air is low RH it should be able to take up more oil evaporation - so it very well could be that too dry air may increase drying of lubricants.

The best RH for photographic equipment storage is between 35% and 50%. I aim for 45%.

 

[koraks]

Thinking of physical class in school, a liquid only can evaporate if the air is warm enough - and not saturated.

Sort of. Evaporation happens also at low temperatures; it's just a slower process. But the degree of saturation in the gas/air on top of the material (not necessarily a liquid) does indeed moderate the rate of evaporation also (i.e. vapor pressure). It's for this reason that on a dry, cold winter's day, ice can actually evaporate - a process called 'sublimation' (which also happens to some other solids; iodine comes to mind).

Taking this back to lubricants:
* Temperature is an important parameter like in all chemical reactions. The hotter it is, the faster it goes.
* W.r.t. RH I doubt it does much. Maybe very high RH (>90%) would slow down any evaporation, but this evidently has significant drawbacks and should be avoided.
* Evaporation of greasy lubricants will happen; the rate of this is dictated primarily by the chemical makeup of the lubricant. Generally, it's only the more volatile parts of the compound product that will separate out and/or evaporate.

I couldn't say whether the difference between 10% and 35% RH would be very significant in this context. I guess it depends on the greases involved and their chemical makeup. Even so, I expect the influence to be minor.

Avoid high temperatures; volatile parts of a lubricant can more easily spread out and wreak havoc this way. I guess we've all seen this happen on old lenses that have gone foggy. Leaving the camera bag in a sunny spot or for extended periods in a hot car would certainly accelerate this.

 

[Lemmythink]

So I can't get the quote to work. Here it is from koraks above

Evaporation of greasy lubricants will happen; the rate of this is dictated primarily by the chemical makeup of the lubricant.

This is the question. But maybe I misunderstand. Here is my thinking: Water based/containing lubes will lose that water fraction in a dry atmosphere. BUT if the lubes are entirely void of water, the water content of the air will not matter. Instead the any vapour from the oil will trend towards achieving an equilibrium in the air, independently of humidity. So if this is the case a really dry air would have no impact on lube drying and be excellent for storage. So the question is - what is the chemical makeup of the lubricants used in photo equipment? Does it contain water or not? I know it's a very specific question but repairers may know.

 

[Sirius Glass]

So I can't get the quote to work. Here it is from koraks above

Evaporation of greasy lubricants will happen; the rate of this is dictated primarily by the chemical makeup of the lubricant.

This is the question. But maybe I misunderstand. Here is my thinking: Water based/containing lubes will lose that water fraction in a dry atmosphere. BUT if the lubes are entirely void of water, the water content of the air will not matter. Instead the any vapour from the oil will trend towards achieving an equilibrium in the air, independently of humidity. So if this is the case a really dry air would have no impact on lube drying and be excellent for storage. So the question is - what is the chemical makeup of the lubricants used in photo equipment? Does it contain water or not? I know it's a very specific question but repairers may know.

Would you have preferred instead of evaporation "lubricant thickening" be used?

 

[Harry Callahan]

Sort of. Evaporation happens also at low temperatures; it's just a slower process. But the degree of saturation in the gas/air on top of the material (not necessarily a liquid) does indeed moderate the rate of evaporation also (i.e. vapor pressure). It's for this reason that on a dry, cold winter's day, ice can actually evaporate - a process called 'sublimation' (which also happens to some other solids; iodine comes to mind).

Taking this back to lubricants:
* Temperature is an important parameter like in all chemical reactions. The hotter it is, the faster it goes.
* W.r.t. RH I doubt it does much. Maybe very high RH (>90%) would slow down any evaporation, but this evidently has significant drawbacks and should be avoided.
* Evaporation of greasy lubricants will happen; the rate of this is dictated primarily by the chemical makeup of the lubricant. Generally, it's only the more volatile parts of the compound product that will separate out and/or evaporate.

I couldn't say whether the difference between 10% and 35% RH would be very significant in this context. I guess it depends on the greases involved and their chemical makeup. Even so, I expect the influence to be minor.

Avoid high temperatures; volatile parts of a lubricant can more easily spread out and wreak havoc this way. I guess we've all seen this happen on old lenses that have gone foggy. Leaving the camera bag in a sunny spot or for extended periods in a hot car would certainly accelerate this.

I see.
The best way to make sure probably was to get a manual for lubricants which are used industrial. There it did matter whether evaporation of oil is dependent on RH or not. Or the manual of an industrial machine.
If oil evaporation was dependent on RH it would say somewhere "re-oil every xx operating hour if RH is 70%, if RH is below 50% re-oil less often" or alike.

So I can't get the quote to work. Here it is from koraks above

Evaporation of greasy lubricants will happen; the rate of this is dictated primarily by the chemical makeup of the lubricant.

This is the question. But maybe I misunderstand. Here is my thinking: Water based/containing lubes will lose that water fraction in a dry atmosphere. BUT if the lubes are entirely void of water, the water content of the air will not matter. Instead the any vapour from the oil will trend towards achieving an equilibrium in the air, independently of humidity. So if this is the case a really dry air would have no impact on lube drying and be excellent for storage. So the question is - what is the chemical makeup of the lubricants used in photo equipment? Does it contain water or not? I know it's a very specific question but repairers may know.

As i said before, i don`t know about this, but would a water-based lubricant make sense at all (in a camera)? Water in a lubricant would evaporate within hours or a few days if applied - i get your idea, but i think the question is if RH does have an impact on oil evaporation.
My take is that air of a certain temperature and humidity only can take up a certain amount of additional molecules - if not saturated already. Air only can carry a certain amount of molecules and if it already is saturated with water molecules it shouldn`t be able to take up even more molecules of oil.
Also oil is "heavier" than water, it won`t evaporate as quick - so saturation of air with water should matter.

 

[koraks]

Instead the any vapour from the oil will trend towards achieving an equilibrium in the air, independently of humidity.

But there's so little lubricant and so much air (even if you put the camera in a bag), that I doubt the vapor pressure of the volatile components of the lube would make much of a difference.

what is the chemical makeup of the lubricants used in photo equipment

It varies. IDK what the different types are, but I expect that in some places, entirely non-volatile lubricants would be used (e.g. graphite) and in other places, it would be greasy/oily lubes. Note that with the latter, it's not just evaporation, but also (mostly) polymerization and perhaps also saponification that play a role in the long term (i.e. 'gumming up'). I would expect these processes to be affected by other factors than moisture.

 

[reddesert]

It seems fungus can be an inevitable thing the older a lens gets. I live in a damp house ...

Fungus is only inevitable or very likely if you live in a damp place (England ...) If one lives in a dry place, it is easier to keep things dry. I live in a hot dry place (southwestern USA) and I haven't seen an effect of low RH on lubricants. Heat has the effect of making lubricants more volatile / migratory, certainly. As far as I can tell in the OP we just have one unattributed statement that RH below 35% will dry out lubricants. I can't see what mechanism would cause this since most lubricants are not miscible with water. Most photo equipment should have very little lubricant on it anyway. The main place I've seen dried out or stiffened lubricant is in lens focusing helicoids, but I don't think it has any relation to RH, just aging of grease.

The reason people don't all store their photo gear in sealed containers with silica gel might be neglect, or that if they use the gear regularly, taking it in and out of the container is a hassle and continually allows fresh humidity into the container. If you can regulate all your storage to 20-30%, go ahead and don't worry about the oil.

 

[Andreas Thaler]

When there is an abrupt change from cold to warm, for example when you come home from a winter trip, moisture condenses.

This can also happen inside lenses if you don't protect them in a camera bag so that the temperature can equalize slowly. And this promotes the formation of fungus.