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PostPosted: Sat Mar 04, 2017 9:14 pm    Post subject: Acetone Reply with quote

Is pure acetone ok to use for cleaning oil off aperture blades?


PostPosted: Sat Mar 04, 2017 9:49 pm    Post subject: Reply with quote

Pure acetone is also nail polish remover, it dissolves acrylic and cellulose nail polish - which is actually paint. It also dissolves the glue that bonds false nails to to real ones. It's a very aggressive solvent.

But....I've used it a lot on lenses, so I guess the paint is enamel which isn't affected? Maybe if the enamel paint is soaked and left, it would soften or dissolve? It might be worth trying leaving a part of a dead lens ( we've all got them Wink ) in some acetone for a while just to test it.
I've never had any issue when using pure acetone nail polish remover, and the best part is - my wife keeps buying it. Like 1 small

Having said that, what I mostly use is cans of lighter fuel that I get from the Pound shop, but I have to buy them myself.

How about this for a deal though ?

http://www.ebay.co.uk/itm/like/321159719958?lpid=122&chn=ps&adgroupid=36165537022&rlsatarget=pla-277568682670&adtype=pla&poi=&googleloc=9041093&device=c&campaignid=738474636&crdt=0



.


PostPosted: Sun Mar 05, 2017 12:23 am    Post subject: Reply with quote

I wouldn't recommend it. As LLoydy says its an aggressive solvent, it will attack many plastics & often remove paint/lacquer.

Lighter fluid or failing that Petrol would be better options, both of which are readily available.


PostPosted: Sun Mar 05, 2017 5:45 pm    Post subject: Reply with quote

Lloydy wrote:

But....I've used it a lot on lenses


David, if it's so aggressive, what do you use it for?


PostPosted: Sun Mar 05, 2017 6:00 pm    Post subject: Reply with quote

DigiChromeEd wrote:
Lloydy wrote:

But....I've used it a lot on lenses


David, if it's so aggressive, what do you use it for?


It excellent for cleaning lab glassware, and if theres no plastic or painted surfaces nearby lenses too - but that normally means taking the elements out of the lens. It's precisely because it's so aggressive that it works well under the right circumstances.


PostPosted: Sun Mar 05, 2017 11:54 pm    Post subject: Reply with quote

My school suggests an escalation of cleaning techniques (if necessary) -- certainly, Acetone, given toxicity and aggressiveness, is among the last resorts.

Acetone is very toxic. Millions (Billions?) of women have been poisoning themselves with Acetone and whatever it removes for a long time...can consider effects of poisonous makeup and removers on fetus to gauge adult effects. Acetone is very hard on kidneys and liver...

Lighter fluid contains benzine, a known carcinogen.

Using these with gloves and respiratory protection, in a well-ventilated area is recommended, only if you absolutely must -- nature also feels the effects...


PostPosted: Mon Mar 06, 2017 9:42 pm    Post subject: Reply with quote

visualopsins wrote:
My school suggests an escalation of cleaning techniques (if necessary) -- certainly, Acetone, given toxicity and aggressiveness, is among the last resorts.

Acetone is very toxic. Millions (Billions?) of women have been poisoning themselves with Acetone and whatever it removes for a long time...can consider effects of poisonous makeup and removers on fetus to gauge adult effects. Acetone is very hard on kidneys and liver...

Lighter fluid contains benzine, a known carcinogen.

Using these with gloves and respiratory protection, in a well-ventilated area is recommended, only if you absolutely must -- nature also feels the effects...


Sorry but that's a lot of balloney about acetone, this may apply when working in industrial plants where solvents are present in excessive concentrations, see the ... The human body even produces small amount so acetone ! So we are poisoning ourselves ? Besides, nail polish remover does mainly contain ethyl acetate which brings the typical smell ... only the "newspeak" el cheapo stuff is based on aceton aka dimethyl keton ... A popular solvent with lens repair people is MEK methyl-ethyl ketone an analogue of aceton ...
https://www.atsdr.cdc.gov/toxprofiles/TP.asp?id=5&tid=1

"Benzine" is a global name to define a cut of light fuel from fractionated distillation of petroleum products. Mostly used as fuel for cars et al. The Anglo-Saxons call it "gasoline". It is highly unlikely that in the concentrations used one will get any ill effects of the small fraction of cyclic compounds present (benzene). But as with all materials that contain solvents, a well ventilated environment is compulsory ...

People should get their facts right/straight and in perspective ... inhaling your average domestic oil paint when painting yr garden fence is a lot more dangerous in terms of solvents inhalation than cleaning a lens in a controlled environment ! .. and of course never use paint brush cleaner solvents as you use these in much larger quantities than the few drops used when cleaning a lens ... Rolling Eyes


PostPosted: Tue Mar 07, 2017 12:06 am    Post subject: Reply with quote

Rigel wrote:

"Benzine" is a global name to define a cut of light fuel from fractionated distillation of petroleum products. Mostly used as fuel for cars et al. The Anglo-Saxons call it "gasoline". It is highly unlikely that in the concentrations used one will get any ill effects of the small fraction of cyclic compounds present (benzene). But as with all materials that contain solvents, a well ventilated environment is compulsory ...



No Anglo-Saxons call the spark ignition fuel 'Petrol', Americans call it gasoline & that is also the 'Proper shipping name' required for sending it internationally. Benzine is I believe the German name for it.

The carcinogenic compound being refered to is actually Benzene (C6H6). IIRC In Europe at least lighter fluid contains less than 0.01% benzene so is not itself classed as carcinogenic. Hydrocarbon products with higher benzene levels are considered Toxic & can't be sold to the general public unless they happen to be called gasoline/petrol etc which is given a special dispensation. (Why the name stops it being toxic is quite beyond me!).
At work we stopped making lighter fluid about ten years ago so I suppose my memory could be out by an order of magnitude but the principles definitely have not changed.

Although the chemicals being suggested are not overly harmful, using them in a well ventilated spot is definitely the right approach.


PostPosted: Tue Mar 07, 2017 12:56 am    Post subject: Reply with quote

The acetone I use is regular nail polish remover, which I have used to clean oil off aperture blades - and it hasn't damaged the plastic or paint on any of the lenses I've used it on. Obviously it might damage some, caution and testing is recommended.

MEK, which has been recommended is something I would not use. As a solvent it is far stronger and is the cleaner used when cementing various types of plastic pipe, and prepping plastics prior to welding ( something I did a lot of in my job as maintenance engineer in the water treatment industry ) - here's a quote from an advert

"MEK Degreasing & Cleaning Fluid. Used for cleaning and degreasing, PP (Polypropylene) & PE Polyethylene Socket Fusion Pipes and fittings prior to welding, UPVC & ABS pipes and fittings prior to solvent welding.
Also for degreasing PP (Polypropylene), HDPE (High Density Polyethylene), MDPE (Medium Density Polyethylene), LDPE (Low Density Polyethylene) and UPVC (Unplasticised Polyvinyl Choride) rigid sheets prior to hot air or extrusion welding"

The important part of that is "prior to solvent welding" the MEK softens the surfaces of the pipe and the pipe fitting allowing the solvent cement to work more rapidly, it's a pre solvent. We had MEK in 5 litre containers on our vans, and inevitably we used it a lot for cleaning, and it was surprising how much stuff was damaged by it, it destroys most paints and affects the surface of many plastics. Interestingly, if we ran out of MEK and used acetone ( which we also had in the workshop for cleaning instruments ) the acetone didn't prepare the pipe joints by dissolving the surfaces as MEK does. It did clean the surface, but we would have to abrade the joint surface to remove the gloss finish to get the solvent cement to work, and even then it was slower and we didn't trust the joints under high pressure.
If some people use MEK to clean lenses and camera components and it does no harm, then I take their word for it - simply because my experience with MEK makes it the last thing I would personally use.

But like I said, I use Pound Shop lighter fuel - naptha - mostly, I bought five 90ml tins last week and that will last me for ages. It's good, and leaves no residue, and doesn't evaporate as quick as acetone or MEK so it's far better to use with a soft artists brush to work heavier grease deposits off, then flush with clean stuff.

I have also used water soluble degreaser / solvents such as Jizer with hot water to clean stubborn grease from helicals. A particularly nasty Helios got boiled in a strong Jizer solution for about 10 minutes and it came out like new.

I haven't tried lens parts in the dishwasher yet, but I have put a Toyota cylinder head in it, and that also came out looking like new! Laughing


PostPosted: Tue Mar 07, 2017 3:44 pm    Post subject: Reply with quote

Facts and fiction ....
http://hyperphysics.phy-astr.gsu.edu/hbase/Organic/ketone.html


PostPosted: Tue Mar 07, 2017 5:42 pm    Post subject: Reply with quote

Rigel wrote:
visualopsins wrote:
My school suggests an escalation of cleaning techniques (if necessary) -- certainly, Acetone, given toxicity and aggressiveness, is among the last resorts.

Acetone is very toxic. Millions (Billions?) of women have been poisoning themselves with Acetone and whatever it removes for a long time...can consider effects of poisonous makeup and removers on fetus to gauge adult effects. Acetone is very hard on kidneys and liver...

Lighter fluid contains benzine, a known carcinogen.

Using these with gloves and respiratory protection, in a well-ventilated area is recommended, only if you absolutely must -- nature also feels the effects...


Sorry but that's a lot of balloney about acetone, this may apply when working in industrial plants where solvents are present in excessive concentrations, see the ... The human body even produces small amount so acetone ! So we are poisoning ourselves ? ...


It certainly does apply in industry! Smile Nail polish remover is cerainly long-term exposure. Certainly the body produces and eliminates tiny amounts normally. Abnormally, people with kidney disease smell of the excess acetone in their bodies; there is keto-acidosis. These are diseased states, not normal.

Suggest checking the MSDS: http://www.hazard.com/msds/mf/baker/baker/files/a0446.htm

Quote:
Potential Health Effects
----------------------------------

Inhalation:
Inhalation of vapors irritates the respiratory tract. May cause coughing, dizziness, dullness, and headache. Higher concentrations can produce central nervous system depression, narcosis, and unconsciousness.
Ingestion:
Swallowing small amounts is not likely to produce harmful effects. Ingestion of larger amounts may produce abdominal pain, nausea and vomiting. Aspiration into lungs can produce severe lung damage and is a medical emergency. Other symptoms are expected to parallel inhalation.
Skin Contact:
Irritating due to defatting action on skin. Causes redness, pain, drying and cracking of the skin.
Eye Contact:
Vapors are irritating to the eyes. Splashes may cause severe irritation, with stinging, tearing, redness and pain.
Chronic Exposure:
Prolonged or repeated skin contact may produce severe irritation or dermatitis.
Aggravation of Pre-existing Conditions:
Use of alcoholic beverages enhances toxic effects. Exposure may increase the toxic potential of chlorinated hydrocarbons, such as chloroform, trichloroethane.


Quote:
8. Exposure Controls/Personal Protection

Airborne Exposure Limits:
Acetone:
-OSHA Permissible Exposure Limit (PEL):
1000 ppm (TWA)

-ACGIH Threshold Limit Value (TLV):
500 ppm (TWA), 750 ppm (STEL) A4 - not classifiable as a human carcinogen
Ventilation System:
A system of local and/or general exhaust is recommended to keep employee exposures below the Airborne Exposure Limits. Local exhaust ventilation is generally preferred because it can control the emissions of the contaminant at its source, preventing dispersion of it into the general work area. Please refer to the ACGIH document, Industrial Ventilation, A Manual of Recommended Practices, most recent edition, for details.
Personal Respirators (NIOSH Approved):
If the exposure limit is exceeded, a half-face organic vapor respirator may be worn for up to ten times the exposure limit or the maximum use concentration specified by the appropriate regulatory agency or respirator supplier, whichever is lowest. A full-face piece organic vapor respirator may be worn up to 50 times the exposure limit or the maximum use concentration specified by the appropriate regulatory agency or respirator supplier, whichever is lowest. For emergencies or instances where the exposure levels are not known, use a full-face piece positive-pressure, air-supplied respirator. WARNING: Air-purifying respirators do not protect workers in oxygen-deficient atmospheres.
Skin Protection:
Wear impervious protective clothing, including boots, gloves, lab coat, apron or coveralls, as appropriate, to prevent skin contact.
Eye Protection:
Use chemical safety goggles and/or a full face shield where splashing is possible. Maintain eye wash fountain and quick-drench facilities in work area.


PostPosted: Tue Mar 07, 2017 6:20 pm    Post subject: Reply with quote

Rigel wrote:
Facts and fiction ....
http://hyperphysics.phy-astr.gsu.edu/hbase/Organic/ketone.html


I'm an engineer, not a chemist so the tech is lost on me Wink but there is a difference between MEK and acetone even if they are both ketone's, which is why they behave differently on the same materials.

I've had some scrap lens parts, internal, external and glass, soaking in acetone for about 24 hours and it hasn't affected the paint, plastic or the lens coating. I haven't got any MEK left, I'm retired and don't have need for it now, but I'll try and get some and try the same experiment, to see if it's OK or not on the same parts.


PostPosted: Wed Mar 08, 2017 3:15 pm    Post subject: Reply with quote

visualopsins wrote:
Rigel wrote:
visualopsins wrote:
My school suggests an escalation of cleaning techniques (if necessary) -- certainly, Acetone, given toxicity and aggressiveness, is among the last resorts.

Acetone is very toxic. Millions (Billions?) of women have been poisoning themselves with Acetone and whatever it removes for a long time...can consider effects of poisonous makeup and removers on fetus to gauge adult effects. Acetone is very hard on kidneys and liver...

Lighter fluid contains benzine, a known carcinogen.

Using these with gloves and respiratory protection, in a well-ventilated area is recommended, only if you absolutely must -- nature also feels the effects...


Sorry but that's a lot of balloney about acetone, this may apply when working in industrial plants where solvents are present in excessive concentrations, see the ... The human body even produces small amount so acetone ! So we are poisoning ourselves ? ...


It certainly does apply in industry! Smile Nail polish remover is cerainly long-term exposure. Certainly the body produces and eliminates tiny amounts normally. Abnormally, people with kidney disease smell of the excess acetone in their bodies; there is keto-acidosis. These are diseased states, not normal.

Suggest checking the MSDS: http://www.hazard.com/msds/mf/baker/baker/files/a0446.htm
...
[/quote]

I wonder if you have any sort of idea what 500/750 or 1000 ppm means ... given the density of 0.785 gr/cm3 you can easily calculate this yourself ...
BTW The LD50 dosis for different "lab" animals is roughly between 3 and 10 gram/kg body weight and by ingestion, which really is a river of solvent ! ... this presumed "danger" of these solvents sounds like the mouse that gave birth to a mountain ... Rolling Eyes oh well ... going shopping in town for an afternoon or having a nice BBQ, is a 1000x more dangerous ... you're "eating"/ingesting benzopyrenes by the spoonful LOL !


PostPosted: Wed Mar 15, 2017 12:36 am    Post subject: Reply with quote

Rigel wrote:
visualopsins wrote:
Rigel wrote:
visualopsins wrote:
My school suggests an escalation of cleaning techniques (if necessary) -- certainly, Acetone, given toxicity and aggressiveness, is among the last resorts.

Acetone is very toxic. Millions (Billions?) of women have been poisoning themselves with Acetone and whatever it removes for a long time...can consider effects of poisonous makeup and removers on fetus to gauge adult effects. Acetone is very hard on kidneys and liver...

Lighter fluid contains benzine, a known carcinogen.

Using these with gloves and respiratory protection, in a well-ventilated area is recommended, only if you absolutely must -- nature also feels the effects...


Sorry but that's a lot of balloney about acetone, this may apply when working in industrial plants where solvents are present in excessive concentrations, see the ... The human body even produces small amount so acetone ! So we are poisoning ourselves ? ...


It certainly does apply in industry! Smile Nail polish remover is cerainly long-term exposure. Certainly the body produces and eliminates tiny amounts normally. Abnormally, people with kidney disease smell of the excess acetone in their bodies; there is keto-acidosis. These are diseased states, not normal.

Suggest checking the MSDS: http://www.hazard.com/msds/mf/baker/baker/files/a0446.htm
...


I wonder if you have any sort of idea what 500/750 or 1000 ppm means ... given the density of 0.785 gr/cm3 you can easily calculate this yourself ...
BTW The LD50 dosis for different "lab" animals is roughly between 3 and 10 gram/kg body weight and by ingestion, which really is a river of solvent ! ... this presumed "danger" of these solvents sounds like the mouse that gave birth to a mountain ... Rolling Eyes oh well ... going shopping in town for an afternoon or having a nice BBQ, is a 1000x more dangerous ... you're "eating"/ingesting benzopyrenes by the spoonful LOL !



No, I'm not sure what you're saying there. 500/750 is 2/3. 1000ppm is 1 part per 1000. Laughing Knowing gr/cc, given volume I could calculate mass, right?

The layman does not have your level of training and experience handling chemicals; she may use it in a way your common sense would never permit you to even think of it! I think for layman there is a balance between my over-zealous warnings and your not-a-big-problem approach.

Is dissolved nail polish carried into the body with the solvent? I guess depends on what is nail polish made from...


Last edited by visualopsins on Thu Mar 16, 2017 3:15 am; edited 2 times in total


PostPosted: Wed Mar 15, 2017 8:28 am    Post subject: Reply with quote

visualopsins wrote:



No, I'm not sure what you're saying there. 500/750 is 2/3. 1000ppm is 1 part per 1000. Laughing Knowing gr/cc, given volume I could calculate mass, right?

The layman does not have your level of training and experience handling chemicals; she may use it in a way your common sense would never permit you to even think of it! I think for layman there is a balance between my over-zealous warnings and your not-a-big-problem approach.

Is dissolved nail polish carried into the body with the solvent? I guess depends on what is nail polish made from...


Yes 1 part in a thousand, or 1 acetone molecule for every 1000 air molecules. It's a reasonably high vapor concentration, but acetone is fairly volatile so its not too difficult to achieve it short term. I'm not sure from memory if the limit is a 15 minute short term one or an 8 hour average, but either way it's intended to reflect someone working with it everyday!

Your over-zealous warnings are more like uniformed scaremongering that can potential encourage the layman to try something different that s actually very much more harmful. With all volatile solvents (other than water perhaps) working in a well ventilated area, and minimizing unnecessary skin contact is best, but beyond that there's no need for getting paranoid, for any that are available to the general public.


PostPosted: Thu Mar 16, 2017 2:59 am    Post subject: Reply with quote

DConvert wrote:
visualopsins wrote:



No, I'm not sure what you're saying there. 500/750 is 2/3. 1000ppm is 1 part per 1000. Laughing Knowing gr/cc, given volume I could calculate mass, right?

The layman does not have your level of training and experience handling chemicals; she may use it in a way your common sense would never permit you to even think of it! I think for layman there is a balance between my over-zealous warnings and your not-a-big-problem approach.

Is dissolved nail polish carried into the body with the solvent? I guess depends on what is nail polish made from...


Yes 1 part in a thousand, or 1 acetone molecule for every 1000 air molecules. It's a reasonably high vapor concentration, but acetone is fairly volatile so its not too difficult to achieve it short term. I'm not sure from memory if the limit is a 15 minute short term one or an 8 hour average, but either way it's intended to reflect someone working with it everyday!

Your over-zealous warnings are more like uniformed scaremongering that can potential encourage the layman to try something different that s actually very much more harmful. With all volatile solvents (other than water perhaps) working in a well ventilated area, and minimizing unnecessary skin contact is best, but beyond that there's no need for getting paranoid, for any that are available to the general public.


1kppm is using number of molecules rather than volumes, really? (For a given volume of air, it takes less acetone in warm air to achieve 1kppm? -- I don't think it works like that. I think it is 1kppm comparing volumes. Sorry I am lost here...)

Someone working with it everyday, such as for nail polish removal, applies way more than 1kppm, and probably breathes fumes for 15 minutes...

Yes, someone might try something very much more harmful such as mixing ammonia and chlorine (don't -- that makes deadly fumes!) but I think my warning could promote the other behavior of using caution with ANY choice, to learn about proper protocol to avoid self-harm.

Myself, I don't use gloves, but I don't get on my hands. I don't use a respirator, but I do use in a well-ventilated area. I use small amounts, drops onto earbuds, usually, although I might soak something -- I might wear gloves for that. It looks like pure water. It should be stored in a container marked (& closed) in some way so to prevent accidental misuse.

Sorry if I freaked out the ladies. I think you especially should be paying attention. Does it make sense to preserve skin by slathering petroleum products or to have good circulation that keeps skin hydrated? You want an old leather bag or something living and vibrant? Indigenous peoples used vegetable and animal fats on the skin sometimes -- not to treat "dry skin", but to protect the skin from the environment, to prevent it from drying out, such as in the wind. Vegetable or Animal fats, not Petroleum byproducts...


PostPosted: Thu Mar 16, 2017 11:34 am    Post subject: Reply with quote

visualopsins wrote:
DConvert wrote:
visualopsins wrote:



No, I'm not sure what you're saying there. 500/750 is 2/3. 1000ppm is 1 part per 1000. Laughing Knowing gr/cc, given volume I could calculate mass, right?

The layman does not have your level of training and experience handling chemicals; she may use it in a way your common sense would never permit you to even think of it! I think for layman there is a balance between my over-zealous warnings and your not-a-big-problem approach.

Is dissolved nail polish carried into the body with the solvent? I guess depends on what is nail polish made from...


Yes 1 part in a thousand, or 1 acetone molecule for every 1000 air molecules. It's a reasonably high vapor concentration, but acetone is fairly volatile so its not too difficult to achieve it short term. I'm not sure from memory if the limit is a 15 minute short term one or an 8 hour average, but either way it's intended to reflect someone working with it everyday!

Your over-zealous warnings are more like uniformed scaremongering that can potential encourage the layman to try something different that s actually very much more harmful. With all volatile solvents (other than water perhaps) working in a well ventilated area, and minimizing unnecessary skin contact is best, but beyond that there's no need for getting paranoid, for any that are available to the general public.


1kppm is using number of molecules rather than volumes, really? (For a given volume of air, it takes less acetone in warm air to achieve 1kppm? -- I don't think it works like that. I think it is 1kppm comparing volumes. Sorry I am lost here...)

Someone working with it everyday, such as for nail polish removal, applies way more than 1kppm, and probably breathes fumes for 15 minutes...

Yes, someone might try something very much more harmful such as mixing ammonia and chlorine (don't -- that makes deadly fumes!) but I think my warning could promote the other behavior of using caution with ANY choice, to learn about proper protocol to avoid self-harm.

Myself, I don't use gloves, but I don't get on my hands. I don't use a respirator, but I do use in a well-ventilated area. I use small amounts, drops onto earbuds, usually, although I might soak something -- I might wear gloves for that. It looks like pure water. It should be stored in a container marked (& closed) in some way so to prevent accidental misuse.

Sorry if I freaked out the ladies. I think you especially should be paying attention. Does it make sense to preserve skin by slathering petroleum products or to have good circulation that keeps skin hydrated? You want an old leather bag or something living and vibrant? Indigenous peoples used vegetable and animal fats on the skin sometimes -- not to treat "dry skin", but to protect the skin from the environment, to prevent it from drying out, such as in the wind. Vegetable or Animal fats, not Petroleum byproducts...


Yes, exposure limits are listed as Molar ppm or in mg/m³ (milligrams compound per cubic meter of air) the two are normally converted using STP (Standard Temperature & Pressure) Having just checked EH40, (The UK's legal listing of airborne exposure limits, available from http://www.hse.gov.uk/pubns/books/eh40.htm) I find Acetone is listed as having a 500ppm TWA which equates to 1210mg/m³ as an 8 hour average, and 1500ppm (3620mg/m³) for short term 15 minute exposures. Interestingly the only compound listed that has a higher STEL is carbon di oxide Smile


PostPosted: Thu Mar 16, 2017 2:44 pm    Post subject: Reply with quote

Well, apart from health issues, I have noted that even simple ethanol has been able to discolour heavily the metal of the flanges of my tamrons.

A pro chemist once told me that glass is usually not damaged by acids (excluding the hydrofluoric one, very dangerous for humans as well).

He told me that he cannot vouch for the safety of any compound with regard to anti reflection coatings: so I think that some experiments should be made with regards to this aspect.

A sad thing I have noticed is that some overcleaning with ethanol tends to embed some tiny sparky dots into lenses, maybe material coming from the very tissue used for cleaning.

They can be usually removed with home alcohol but sometimes they stay.

I have not noticed any bad effects by hydrogen peroxyde, ammonia or isopropyl, but the latter tends to freeze leaving halos that are difficult to remove (it freezes at room temperature I was told).

The more I clean a lens the worst it is, actually. Also special paper, glass cleaning tissues or fiber cloth get quickly dirt, after a couple passes or so they tend to transfer dust to the lens.

An industrial way of cleaning seriously lenses is the peeling polymers or triple collodion method (my translation of italian terms, it is based on a plastic liquid film that is laid on the lens, the alcohol part then evaporates, the resulting solid film is lifted carrying away all dirt leaving the lens perfectly clean) but so far I have been unable to find the compound in pharmacies or lab services.

As long as a serious source of such polymers is not available to me I will refrain from cleaning groups, barring the ones with fungus.

It is ever better to clean disassembled lenses, if necessary, otherwise dirt from surrounding flanges could be dislodged by solvents ending up on the lens.

Obviously the real problem in a lens is the glass lenses. metals tend to be strong, if burnishing goes away the part will work flawlessly: some reflections will likely be introduced but to a moderate extent. Apart from diaphragm blades, for which burnishing is obviously important. In exteme cases a gun repairer might chemically burn them again with a low expense I guess. Weapons can be burnished also at home with cheap chemicals, so it could be made for blades as well


PostPosted: Thu Mar 16, 2017 10:12 pm    Post subject: Reply with quote

Lloydy wrote:
Rigel wrote:
Facts and fiction ....
http://hyperphysics.phy-astr.gsu.edu/hbase/Organic/ketone.html


I'm an engineer, not a chemist so the tech is lost on me Wink but there is a difference between MEK and acetone even if they are both ketone's, which is why they behave differently on the same materials.

...


FWIW ... short cut ... The polarity index for acetone is 5.1 and that for MEK is 4.7 which, theoretically, makes acetone the "stronger" solvent.


PostPosted: Thu Mar 16, 2017 11:39 pm    Post subject: Reply with quote

Rigel wrote:


FWIW ... short cut ... The polarity index for acetone is 5.1 and that for MEK is 4.7 which, theoretically, makes acetone the "stronger" solvent.


Polarity Index gives an indication of the strength of a solvent for polar compounds, but for non polar compounds the effect is the other way round. When trying to dissolve hydrocarbon oils & greases MEK is a stronger solvent because of it's lower polarity. Acetone does a reasonable job of dissolving lighter hydrocarbons, but starts to struggle a bit with material boiling around the same range as diesel. In cleaning lab glassware used for heavier materials I generally use a lighter hydrocarbon sample, prior to acetone flushing.

There are actually further factors than just polarity in solvency as well but I wouldn't expect things like lone pair acceptance/donation to vary significantly between these two chemicals. In gas chromatography there where 5 marker compounds chosen to characterize the solvency interactions of stationery phases, these five where later extended to ten to fully characterize solvency. For general cleaning purposes such minor differences are probably fairly irrelevant, but like for like polarity is certainly going to give the best solvency.


PostPosted: Fri Mar 17, 2017 1:09 pm    Post subject: Reply with quote

To answer the question: use COLEMAN FUEL/similar to clean the iris blades. Thats what I used on a vivitar 70-210mm.
There are some good descriptions of iris blade cleaning in the tech notes for the lenses on Boggy's.

http://www.boggys.co.uk/page44.html


PostPosted: Fri Mar 17, 2017 5:10 pm    Post subject: Reply with quote

Thanks to DConvert and Rigel for the helpful Chemistry lessons!


PostPosted: Wed Mar 22, 2017 7:38 pm    Post subject: Reply with quote

What about disposal?

After the discussions here, the dissolved substances seem to be much more of a problem than the Acetone itself. In labs & industry the Acetone is recovered & recycled. What about the sludge leftover?


PostPosted: Thu Mar 23, 2017 5:08 pm    Post subject: Reply with quote

I clean aperture blades exclusively with naphtha. I also reserve such work for warm weather, when I can do it outdoors. So, I will accumulate lenses over the winter and then in April/May I go on cleaning binge. As to the disposal, I change my own oil, so there's always a container I can dump it in.


PostPosted: Sun Aug 06, 2017 5:55 am    Post subject: Reply with quote

It's rare, but some blades and aperture components are painted -- naphtha is your preferred solvent for cleaning oil which has migrated into the aperture mechanism. Acetone is fine for cleaning most lens elements.