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Ethanol or methanol for sensor cleaning

Vandit Kalia , May 02, 2006; 02:36 a.m.

Most of the recommendations I see here for sensor cleaning tend to involve methanol.

Yes, one of the websites (the guys that market Eclipse) recommend using ethanol over methanol.

Anyone know if one is better than the other for sensor cleaning?

I am going to be using it with Pecpads and a Sensor Swipe that I have ordered from Copperhill. Cannot get Eclipse shipped to where I am, so have to source locally.

Vandit

Responses


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Vladimir Anisimov , May 02, 2006; 03:57 a.m.

Good question. I know that one can actually drink ethanol (aka alcohol), unlike methanol which is harmful to humans. Do cameras care?.. that's the question

Peter Meade , May 02, 2006; 04:28 a.m.

Methanol is a very powerful solvent and can dissolve silica, depending on what the sensor is protected with, you risk ethching it. I would stear clear of that.

Ethanol is may be denatured with some other chemicals to stop you from drinking it, so if it smells of anything don't tuch it, you risk leaving a deposit on the sensor cover. A good option is isopropyl alcohol (propan-2-ol), which is a lot less agressive and is relatively non toxic.

Vandit Kalia , May 02, 2006; 05:53 a.m.

A clarification:

- actually, the recommendation against using methanol was from Visible Dust: http://www.visibledust.com/faq.html#15

Peter & Vladimir - the recommendation against methanol was precisely b/c of its strong and potentially corrosive nature.

However, Eclipse is supposed to be methanol-based and almost every site cleaning website mentions using methanol.

Peter, I'll try isopropyl alcohol - I assume that is also residue free, just like 99.5% ethanol? Anyone here who has used either of these for cleaning the sensor and can provide a first-hand account of the experience?

Vandit

Walter Schroeder , May 02, 2006; 08:03 a.m.

I would avoid liquids on a sensor for regular cleaning and only use it if everything else fails. If you really need a liquid i would follow Peters advise with isopropyl alcohol. Make certain that no liquid can get to other surfaces like between sensor and filter. (Normally "sensor cleaning" is cleaning the filter in front of the sensor.)

Conrad Hoffman , May 02, 2006; 09:07 a.m.

In the grand scheme of things, none of these are wildly different. Yes, methanol can attack epoxies, but it takes near to forever to do so. Methanol is extremely effective at removing old fingerprints, but the others are good enough. The real problem is getting any solvent in a purity high enough so as not to leave a film or residue. If I can find it pure enough, I prefer acetone, but watch out for plastics and painted surfaces. When ordering from a lab supply house, you want what's referred to as "spectroscopic grade". Anything you can get at the druggist or hardware store will be inferior. OTOH, if you don't know how to handle it, it won't be spectroscopic grade 30 seconds after you open the bottle and touch the top with a cloth or tissue. If you can find 91% or better pure isopropyl, that's reasonably safe and inexpensive. Everclear is supposedly a good choice, though I've never tried it. I wouldn't use methanol unless nothing else was effective, mostly because of toxicity. OTOH, if it were all that was available, I wouldn't hesitate to use it carefully. Caution- there may be differences in sensors, coatings, and construction, so any of these are at your own risk!

Kevin Conville , May 02, 2006; 01:02 p.m.

I've used labratory grade isopropyl. This is available from electronics supply stores and is 99.953 % pure.

Using a Q-tip dipped in the alcohol them rolled lightly in a Kleenex (white, unscented only), small flashlight in hand to see well, using the lightest pressure, this works well and quickly to remove things that don't blow off.

Bob Atkins , May 02, 2006; 01:17 p.m.

Methanol is a very powerful solvent and can dissolve silica, depending on what the sensor is protected with, you risk ethching it. I would stear clear of that.

Absolute crap I'm afraid, and I'm speaking here as someone with a Ph.D. in chemistry. Methanol is actually a fairly mild solvent. It's harmless to most plastics and totally harmless to glass and silica. It's excellent for cleaning optics, in fact it's the preferred solvent for the cleaning of very delicate laser optics, which are WAY more delicate than anything you'll find in a camera. Methanol is also quite good at disolving inorganic materials as well as orgainics, so it will remove things like salt (left over from fingerprints) as well as orgainics like grease (left over from fingerprints!).

The only downside of methanol is that it is toxic to humans, though you need to drink it or chronic exposure to do much harm. Using it to ocassionally clean optics is safe. Just don't drink it, take a bath in it or breath the fumes for hours each day.

Ethanol is actually a better solvent for organic materials, and again it's safe on most plastics and all glasses. It's also toxic in very large doses, though obviously not immediately a problem in small doses!

Bottom line - use ethanol or methanol, depending on what you have or what you can easily get. They're quite similar and both will be fine for sensor cleaning. Just make sure they are pure and leave no residue on evaporation.

The solvent to avoid is Acetone. It's a very, very good solvent for organic materials like grease - and most plastics, glues and paints. The problem with it is that it may dissolve the inside (and outside) of your camera it it comes into contact with it. It's also toxic in large enough doses. Unless you've poured hot tar on your sensor, you don't need Acetone!

I have a general article on optics cleaning HERE

Edward Ingold , May 02, 2006; 01:29 p.m.

The main problem is getting a solvent with high purity so that it does not leave a residue, and one that does not readily degrade. The main use in cleaning sensors is to make dust particles stick to the cleaning pad, and only partly to remove other contaminents. A few drops are placed on the cleaning pad, and very little is actually deposited on the sensor.

Methanol is not an especially agressive nor corrosive solvent. It is readily available with extremely high purity for spectrographic or chromatography use. Methanol is widely used to clean laboratory optics. It has no effect whatsoever on glass - I have no idea where that "factoid" comes from. The chief contaminant of methanol is formaldehyde, which condenses in time to form paraformaldehyde, which would leave a white residue. Perhaps that is the source of this rumor. Methanol does not oxide readily to formaldehyde, so the initial purity is the most important factor.

Ethanol is hard to find with sufficient purity, due to tax reasons more than anything else. Isopropyl alcohol is a mild solvent, less polar than methanol, and would probably work. Again, the purity is an issue. Isopropyl tends to bead on glass and is slow to evaporate, and may pick up atmospheric contaminants in the process of drying.

I strongly recommend against using acetone anywhere near a lens. It attacks most resins aggressively and is usually contaminated with paraldehyde, which (like paraformaldehyde) leaves a white residue. Paraldehyde is a condensation product which forms on storage.

Vivek . , May 02, 2006; 01:32 p.m.

Bob, As another Chemist, I am surprised that you made the assertion.

Peter Meade is correct. Methanol does dissolve silica gel.

If you have done any column chromatography of natural products, you may recall that methanol was used as a final flush (being most polar). But any fractions needed to be reextrated with a non alcoholic solvent after evaporation of methanol because of the silica gel it brought down with it.

I can confirm that the Eclipse cleaning fluid does dissolve the low pass filter in my D70 and after every clean I can clearly see the blue-green color on the swab.

Just to confirm this, I tried the same fluid (Methanol) on various deep colored bandpass filters (R800, U-330 and the like)and yes there was deep red colors coming off of the filters. With a blue-green filter like the Schott BG-38 or BG-39 (similar to the low pass filter in D70/70s/50), there was blue coloration.

I switched to i-Propanol (iso-Propanol) which is less polar and hence less "corrosive".


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