Cleaning plexi crystal in isopropylalcohol

[alalalalongines]

Hello everybody.

Yesterday i tightened a canon pinion and also cleaned the case.
After cleaning the case (including the crystal) in lighter fluid and rinsing it case in isopropylalcohol i noticed fine concentric hairlines in the crystal, that are so fine making it impossible to photograph.

Have i damaged the crystal this way or were they there before and i haven't noticed them because they are so small?

Thank you for your attention.
Have a nice day!
Lukas

 

[STANDY]

Who told you to clean the case in lighter fluid and then alcohol….dishwashing soap and water is usually all you need…


We definitely need pictures

 

[alalalalongines]

STANDY

Who told you to clean the case in lighter fluid and then alcohol….dishwashing soap and water is usually all you need…


We definitely need pictures

I thought there was less chance of rust if i don't use water.
Thank you for the tip. But it does not answer my question if the IPA is to blame.

You can see the hairlines over the hour hand.

 

[Dan S]

The IPA may have made the crazing more visible if it seeped in and increased the refractive index contrast. But ultimately only you can tell us if the crazing was present previously. We don't know.

 

[gatorcpa]

A alalalalongines

Have i damaged the crystal this way or were they there before and i haven't noticed them because they are so small?

Both.

https://www.watchuseek.com/threads/alcohol-and-acrylic-crystals-do-not-mix.1049854/

I think the culprit in the thread I posted are the additives in rubbing alcohol. The threat is less with higher quality alcohol (sometimes called “denatured”).

But if the stress cracks were already present in the crystal, even a successful cleaning is going to make them seem more prominent because you are removing the other distracting scratches on the surface.

The only cure is a new crystal.
gatorcpa

 

[alalalalongines]

gatorcpa

Both.

https://www.watchuseek.com/threads/alcohol-and-acrylic-crystals-do-not-mix.1049854/

I think the culprit in the thread I posted are the additives in rubbing alcohol. The threat is less with higher quality alcohol (sometimes called “denatured”).

But if the stress cracks were already present in the crystal, even a successful cleaning is going to make them seem more prominent because you are removing the other distracting scratches on the surface.

The only cure is a new crystal.
gatorcpa

Thanks a lot! This post explained it quite well.

 

[Archer]

Alcohol will not damage an acrylic crystal...







No difference before to after applying 99% alcohol to this old acrylic crystal...

 

[kaplan]

I recently got some experience with acrylic, more than I want, replacing around 30 crystals, one watch/crystal combo really wore me down and I got to test and go beyond the limits

Acrylic is a wonder material to me now

I think the main issue here is in the wonder, it's an extremely flexible material and there can be cracks that you can't see under magnification, so maybe the issue is related to this, if the acrylic is used or abused, it could be prone to discolouration or similar issues

As an unproved caution, these invisible cracks can move humidity and ruin a dial - I've seen 2 watches with patinated dials and the crystal was the only culprit, the caseback and the movement was clean and on one of them, the crack was easily observable as the crystal separated while pressing it out, but on the second one, the crystal was strong yet the discolouration path of the water movement inside could be seen

Edit: So maybe if the objective is water proofing, alcohol could be a test material too, if it fogs the acrylic, maybe it's detecting these cracks/zones

 

[Pvt-Public]

A alalalalongines

After cleaning the case (including the crystal) in lighter fluid

If anything thing I would think lighter fluid would be many times worse on acrylic than alcohol. Especially since soap and water is all that’s needed.

 

[Dan S]

The solvent compatibility of PMMA is not a mystery, it is tabulated and readily available. As you can see, it has excellent compatibility with organic alcohols and hydrocarbons.

https://marketing.industrialspec.co...mma-chemical-compatibility-chart-from-ism.pdf

 

[gbesq]

Archer

Alcohol will not damage an acrylic crystal...







No difference before to after applying 99% alcohol to this old acrylic crystal...

Agreed. I use eyeglass lense cleaner to remove dirt and smudges from my crystals. The main ingredient is alcohol and I've been using it for years. Never any damage.

 

[wrist time]

My guess is a case of environmental stress cracking. Either the lighter fluid or the alcohol could have been a factor. No way to know which.
https://en.wikipedia.org/wiki/Environmental_stress_cracking

 

[VictorAlpha]

I'm sorry to revive an old thread and I haven't been around for a long time due to life in general, but the same thing happened to me with more dramatic results. I replaced a dive watch saphire crystal with a Sternkreuz ATCT acrylic. I needed to give it a quick clean and used some iso aclohol. I hear a rather loud crack and on examining the crystal saw what apeared to be a fracture in the sidewall. The crystal separated just above the tension ring and dropped out leaving the rim behind!

I thought it might have been that that the crystal was somehow not properly sized so I went through the excercise again measuring the seating diameter and matching it up with a crystal a tenth or two oversize. Worked great, passed my initial water resistance checks no problem, applied alocohol as an experiment, and crack! Same thing happened. Researched it and it appears that alcolhol negatively affects acrylic and seems to be more pronounced when under tension. Anyway I never take alcohol near an acrylic crystal now, and the watch I installed the acrylic on has been going strong for at least three and a half years now.

 

[kaplan]

VictorAlpha

I'm sorry to revive an old thread and I haven't been around for a long time due to life in general, but the same thing happened to me with more dramatic results. I replaced a dive watch saphire crystal with a Sternkreuz ATCT acrylic. I needed to give it a quick clean and used some iso aclohol. I hear a rather loud crack and on examining the crystal saw what apeared to be a fracture in the sidewall. The crystal separated just above the tension ring and dropped out leaving the rim behind!

I thought it might have been that that the crystal was somehow not properly sized so I went through the excercise again measuring the seating diameter and matching it up with a crystal a tenth or two oversize. Worked great, passed my initial water resistance checks no problem, applied alocohol as an experiment, and crack! Same thing happened. Researched it and it appears that alcolhol negatively affects acrylic and seems to be more pronounced when under tension. Anyway I never take alcohol near an acrylic crystal now, and the watch I installed the acrylic on has been going strong for at least three and a half years now.

Thanks for the experiment

As it stands, I only hand clean and polish crystals, and only rinse with warm water and weak soap and retry as much as I need to until I have a clear view

Dan S

The solvent compatibility of PMMA is not a mystery, it is tabulated and readily available. As you can see, it has excellent compatibility with organic alcohols and hydrocarbons.

https://marketing.industrialspec.co...mma-chemical-compatibility-chart-from-ism.pdf

Just saw this and it's eye opening as well

 

[sheepdoll]

Crystals can not take high heat. Recently I took a paint stripper gun to two of them. I thought perhaps the surface would reflow. Instead they melted, well shrunk and distorted.

Back when I was taking the jewelry (high temperature enamel painting) I tried slumping microscope slides and LCD crystals to see if I could replicate a glass crystal. I think these may be borosilicate (Pyrex) as the normal glass melt temperatures had no effect.

I suspect crystals are made with injection molding. using highly polished dies. One can cast resins (used to encapsulate seashells) Perhaps there might be some way to copy a crystal using rtv. Probably start with the inside mold. The outside could be sanded down and polished.

The laser cutter cuts acrylic nicely. But not poly-carbonate. Might be possible to cut a blank, then machine and polish it. Acrylic does not machine well, it tends to chip. So one would need to use some sort of sanding grinding.

 

[kaplan]

In Turkey they copy crystals with resin, I don’t know the exact process but it was very cheap and the result was incredible, I assume it’s casting + polishing

Makes more sense for old vintage watches though, I gifted a problematic Super Seiko to my brother and the entire restoration with servicing was sub $100

 

[mseamaster]

Archer

Alcohol will not damage an acrylic crystal...







No difference before to after applying 99% alcohol to this old acrylic crystal...

I used 99% ethyl alcohol on my Omega 131.019 crystal and I don't see any issues. Thanks for confirming it here though.

 

[DrSpock]

Maybe the chance for me to ask:
Is it possible to get old NOS crystals (40-50 years old) “soft” again? In the past a watchmaker told me that one of my NOS crystals cracked while trying to fit it onto the watch..

 

[billiout]

Just sharing my experience with an acrylic crystal and alcohol. I have an old Seiko watch from the early 60s that requires a specific and quite rare acrylic crystal to function properly. I was fortunate to find a genuine NOS one. During a recent service, my watchmaker accidentally spilled a small drop of glue on the crystal and attempted to clean it with 99% alcohol. He mentioned that the crystal immediately developed cracks upon contact with the alcohol. He emphasized that he had never encountered this issue with alcohol before (he's a very experienced, old-school watchmaker). Nonetheless, this experience has made me cautious about cleaning vintage acrylic crystals with alcohol whenever possible.

 

[mseamaster]

billiout

Just sharing my experience with an acrylic crystal and alcohol. I have an old Seiko watch from the early 60s that requires a specific and quite rare acrylic crystal to function properly. I was fortunate to find a genuine NOS one. During a recent service, my watchmaker accidentally spilled a small drop of glue on the crystal and attempted to clean it with 99% alcohol. He mentioned that the crystal immediately developed cracks upon contact with the alcohol. He emphasized that he had never encountered this issue with alcohol before (he's a very experienced, old-school watchmaker). Nonetheless, this experience has made me cautious about cleaning vintage acrylic crystals with alcohol whenever possible.

Interesting.. Are you sure it's acrylic btw?

I've always wondered what's on KS/GS watches. I've read it's hardlex which I am starting to doubt now. Perhaps it's just acrylic.