Cleaning dirty DIC prisms

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Wes
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Cleaning dirty DIC prisms

#1 Post by Wes » Wed Sep 04, 2019 5:29 pm

I don't want to screw this one up. Basically I have a DIC objective prism for the Zeiss 160 mm series and its smudged with some greasy looking dirt which I want to remove. What solvent and cleaning tool should I use here. A Q-tip and petroleum ether? Alcohol? Definitely not acetone I'd imagine. I have no clue whether there are special coatings on the prism surface but I'd absolutely avoid the getting the solvent to come into contact with the cemented seams.

MicroBob
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Re: Cleaning dirty DIC prisms

#2 Post by MicroBob » Wed Sep 04, 2019 6:04 pm

Hi Wes,
I would first remove dust with a fine brush. Since you say it's greasy I would continue with lighter fluid and a Q-tip. The Q-tips I use are for workshop purpose (Farnell or RS Components) with a wooden stick and a cotton tip that doesn't disintegrate too soon. Fresh out of the bag they are quite hard and too round to reach into corners. For this reason I take a tissue and grip the tip of the Q-tip trough it and pull it apart and to th side somewhat. This makes it much softer and improves the form without transferring grease from the fingers onto them. Then without real pressure once over the surface, then change Q-tip and repeat. Don't grind the lenses with dust, change frequently.

Perfectionists use "Wundbenzin" https://www.amazon.de/Wundbenzin-hochre ... way&sr=8-2

and "Augenwatte" https://www.medizinfuchs.de/augenwatte.html,
wound around a stick.

Don't worry, your Zeiss prisms will delaminate anyway, sooner or later! :lol:

Bob

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75RR
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Re: Cleaning dirty DIC prisms

#3 Post by 75RR » Wed Sep 04, 2019 6:05 pm

I used isopropanol and cotton wool to remove my fingerprints from the prisms on my DIC sliders.

No harm that I could tell came from the operation and it did remove the fingerprints.

I think there is probably some glass protecting them.

Still, second or even third opinions probably called for in this case ... best to be safe!
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viktor j nilsson
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Re: Cleaning dirty DIC prisms

#4 Post by viktor j nilsson » Wed Sep 04, 2019 6:13 pm

DIC prisms (Wollaston or Nomarski) are simply two very precisely made wedges of quartz or calcite that are cemented together with some sort of optical cement. Not sure what crystal and cement Zeiss used, though. If it's quartz (hardness: 7), it's really hard and I imagine very hard to damage when cleaning carefully. If it's calcite (hardness: 3) you probably should be more careful.

I'm not sure if they are coated, but the Nikon Nomarski prisms I have don't look like they are coated.

Anyway, DIC prisms aren't made out of anything more exotic and fragile than optics in general.

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Re: Cleaning dirty DIC prisms

#5 Post by Wes » Wed Sep 04, 2019 6:52 pm

Many thanks Bob, 75' and Viktor!

I used wundbenzin (petroleum ether) and tightly packed cotton swabs and removed the grease, there are still tiny dot-like specks here and there which are trickier so I just left them for now. I am happy to say I finally found a matching prism for my Jena Apo 40/0.95 lens, much better contrast compared to the 63/1,4 I used so far and a very neat homogeneous field
MicroBob wrote:
Wed Sep 04, 2019 6:04 pm
Don't worry, your Zeiss prisms will delaminate anyway, sooner or later!
A very disturbing thought I have to say! Oh well.. C'est La Vie

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Re: Cleaning dirty DIC prisms

#6 Post by MicroBob » Wed Sep 04, 2019 7:52 pm

What is left after this cleaning might be water soluble.
I would keep the prisms above 20°C - this seems to reduce the risk of delamination.
Some kind of statistic: Of 4 analyser and 8 condenser prisms of the DIC "alt" components 1 analyser prism has slight delamination at the border (after 50 years).

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Re: Cleaning dirty DIC prisms

#7 Post by 75RR » Thu Sep 05, 2019 4:42 am

I am happy to say I finally found a matching prism for my Jena Apo 40/0.95 lens, much better contrast compared to the 63/1,4 I used so far and a very neat homogeneous field
Thanks for the update. Which one did you use and which way round?
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Wes
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Re: Cleaning dirty DIC prisms

#8 Post by Wes » Thu Sep 05, 2019 5:09 am

75RR wrote:
Thu Sep 05, 2019 4:42 am
Which one did you use and which way round?
Its the prism for 40/0,75 water immersion achroplan and I only tried it in its normal orientation.

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Re: Cleaning dirty DIC prisms

#9 Post by 75RR » Thu Sep 05, 2019 5:12 am

Should have guessed it was one I did not have ;)
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Wes
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Re: Cleaning dirty DIC prisms

#10 Post by Wes » Thu Sep 05, 2019 6:13 am

I guess the plan 40/0,65 prism would work as well based on what Jochen told me once. Multi-immersion Neofluar 40/0,9 prism is probably the best as it most closely matches the NA so I figured the 40/0,75 should be close enough.

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75RR
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Re: Cleaning dirty DIC prisms

#11 Post by 75RR » Thu Sep 05, 2019 6:21 am

Can you list your sliders?


This is the full list:
Note: It now appears that this list is missing the Plan Neofluar 40x/0.90 w - oil
Attachments
DIC-Sliders().jpg
DIC-Sliders().jpg (33.53 KiB) Viewed 552 times
3 DIC Sliders.jpg
3 DIC Sliders.jpg (97.11 KiB) Viewed 552 times
Last edited by 75RR on Sat Sep 07, 2019 7:50 pm, edited 1 time in total.
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Wes
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Re: Cleaning dirty DIC prisms

#12 Post by Wes » Thu Sep 05, 2019 6:33 am

Mine are the same except for the 40x one.

That list is missing a couple of sliders, here is a more complete list I found on ebay once (open in a new tab for higher resolution).

Image

And I made mistake, its not achroplan but an achromat.

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75RR
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Re: Cleaning dirty DIC prisms

#13 Post by 75RR » Thu Sep 05, 2019 8:33 am

Thanks for the list.

Only see one extra slider compared to my list which I have highlighted in yellow.

What is really interesting (well potentially so) are the condenser prisms. Adding one of the others to the third port could potentially open the door to more "mismatched" objectives working with the sliders.
Attachments
Sliders & Prisms.jpg
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Re: Cleaning dirty DIC prisms

#14 Post by ImperatorRex » Thu Sep 05, 2019 10:27 am

From my experience the different Wollastan Prismns itself do no lead to new working combinations. I never found such generation good combinations.

A new variable to consider is a different Frontlense like the 0.9 n.A. Frontlense. It provides sometimes new combinations with sliders not foreseen by Zeiss. This statement is valid for Zeiss DIC New and Old.

Wes
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Re: Cleaning dirty DIC prisms

#15 Post by Wes » Thu Sep 05, 2019 6:52 pm

75RR wrote:
Thu Sep 05, 2019 8:33 am
Only see one extra slider compared to my list which I have highlighted in yellow.
You're right, I stand corrected.
ImperatorRex wrote:
Thu Sep 05, 2019 10:27 am
From my experience the different Wollastan Prismns itself do no lead to new working combinations. I never found such generation good combinations.

A new variable to consider is a different Frontlense like the 0.9 n.A. Frontlense. It provides sometimes new combinations with sliders not foreseen by Zeiss. This statement is valid for Zeiss DIC New and Old.
Thanks for sharing Jochen. I don't think I've seen this front lens so far other than in old Zeiss catalogues.

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Re: Cleaning dirty DIC prisms

#16 Post by MicroBob » Fri Sep 06, 2019 10:00 am

Hi together,
from the interesting documents you show here I would conclude that the development from Zeiss DIC old to new was to get a system that is set up for all objectives at the same time and you can swap between them without changeing the DIC setup -right?
With Zeiss DIC old you were using 4 prisms in the condenser, usually changeing between 3 of them. With DIC new you used mainly 1 condenser prism and had your sliders set up for each objective.

That of cause gives great repeatability for routine work. And a technician can set up the microscope for somebody else to use.

Bob

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