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SudoHalt

Replacing Mineral Crystal with Acrylic? Which Size?

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Hey there,

I accidentally cracked the crystal on my Mondaine watch, and I would like to replace the original mineral crystal with Acrylic. The Original crystal is friction fitted into a plastic gasket.

On my vernier calipers, the Original crystal measured at 38.2mm. I have a simple Crystal/Back Cover Press to insert a new crystal, but I assume this approach would be best for replacing with Mineral or Sapphire.

  • Can I use a Crystal Press to friction fit acrylic crystals? Is there a difference in the approach when the new acrylic crystal is flat, low-domed, or high-domed?
  • I am somewhat confused as to the size of the replacement Acrylic Crystal... Do I go with the same size? If not, how much larger?

Thanks!

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You can press an acrylic crystal with a tension ring. For example GS Diver Tite. I would go with a 38mm or 38.1mm. Because if you dont you will never be able to press it in since it expands when pressed and in some case tension ring slips out.

GS Lo/Hi dome can be compressed in using a brass jaw type crystal remover. In this case you will need to go 38.4mm because the jaws grip the crystal and it compresses it then when set into the bezel or case the jaws are released expanding the crystal to set in the case.

flat crystals will need to be glued and any acrylic crystal can be glued except tension ring crystals.

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4 hours ago, SudoHalt said:
  • Can I use a Crystal Press to friction fit acrylic crystals? Is there a difference in the approach when the new acrylic crystal is flat, low-domed, or high-domed?

Yes, with the correct dies. See attached STK document about fitting "snap-in" crystal with a press as opposed to a jaws tool (crystal lift).

8836_Sternkreuz R19 Snap In Glasses Pages 12 to 29.pdf

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Wow thanks a lot!

I got a bunch of homework to do on this... based on what I am understanding, the Acrylic crystals with tension rings could be press-fitted with the crystal press given that we use the correct size of dies, and those crystals would do fine without that plastic gasket, isn't it?

What I am confused about is the plastic gasket that was used to friction-fit the mineral crystal in place. Do I remove it before fitting the acrylic crystal? If yes, then I believe that I have to measure the new diameter of the "dial compartment".

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I have actually went over that guide. However I am still confused about the sizing choice of acrylic crystal if the watch was designed originally to go with Mineral Crystal.

What I am trying to say is... which one of these is true?

  1. I can fit the acrylic crystal into the case using the gasket that came with the original mineral crystal. Could the crystal gasket break or wear out during the assembly of the acrylic?
  2. I need to remove the original gasket and fit the acrylic crystal without a gasket. I have heard that Acrylic crystals could provide decent waterproofing without a crystal gasket.

 

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Hi  If you are going to replace the mineral crystal with an acrylic one without the gasket it is possible but you will need to measure the case seating of the watch and what ever the measurement is add 0.01 but you will need a claw insertion tool and pick up table to do that and also probably some glue/sealant to put round the case, Usually somthing like Minicol UV curing cement to ensure water resistance.

May I ask what is the reason for the change as the minerals are harder and scratch resistant,  acrylics pick up lots of marks but they can be polished out in in most cases.

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Thanks guys! For now that sounds good to me. I will post back here if I have any questions or trouble.

I am considering Acrylic crystals because they are more shatter resistant than both mineral crystals and Sapphire. Yes, acrylic crystals are brittle, so when you drop them they could develop a crack, but Acrylic crystals don't shatter and fall apart when they crack.

It is nowhere as hazardous when cracks happen as fragments will not fly around when a crack happens, and they can maintain a slight degree of splash resistance.

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2 hours ago, SudoHalt said:

I am considering Acrylic crystals because they are more shatter resistant than both mineral crystals and Sapphire. Yes, acrylic crystals are brittle, so when you drop them they could develop a crack, but Acrylic crystals don't shatter and fall apart when they crack.

It is nowhere as hazardous when cracks happen as fragments will not fly around when a crack happens, and they can maintain a slight degree of splash resistance.

Really? I have not see any reports or mineral glass crystals shattering so terribly. The expected use of a dress watch should not involve such potential destructive shocks.
I would not replace a mineral glass with acrylic, but I would replace it with sapphire, because scratching is the actual, common and annoying occurrence.

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Ok  you have your reasons and i stand by that, but I agree with jdm I have not seen a mineral shatter except under extreem circumstances like being dropped onto a hard surface, but I have also seen acrylics crack under the same circumstances.  Cheers.

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52 minutes ago, rodabod said:

I've actually had a sapphire shatter before, never mind a plain mineral glass. That's why acrylic are almost always used for military watches.

Actually mineral glass is more resistent to impact than sapphire. That's why is still fitted to some true diver's watches, a choice that raisises criticism by some.

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4 hours ago, jdm said:

Actually mineral glass is more resistent to impact than sapphire. That's why is still fitted to some true diver's watches, a choice that raisises criticism by some.

That's interesting to know. CWC use plain mineral glass on their divers, but it is very, very thick.

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After assessing my options, I decided with gluing acrylic rather than a "pressable" one with a tension ring. There's no local shop around me that offers acrylic with tension ring, let alone the correct dimensions. I had to sand down the acrylic crystals I got to make them the right size. I used GS crystal cement to get things going, and so far so good. It's also by far the cheapest option as I barely needed any tools for the job.

The only thing I still find ambiguous is, how tough is it to remove the crystal in case I want to replace it in the future? And how hard is it going to be to clean up after the glued crystal is removed?

I just applied the acrylic treatment to my roommate's watch. He coincidentally broke his mineral glass when I started this thread a while ago.

Thanks a lot for the advice given.

 

20200224_170909.jpg

Edited by SudoHalt

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Sounds good! This will go well with the Mondaine! In case of something like the above Casio though, I suppose the buttons got gaskets to maintain some degree of water resistance. Would that affect them?

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Hi     warming the case  is just that not heating as such. The Idea being just to soften the adheisive enough to enable removal, The pusher/button gaskets are usually silicone rubber so should not be affected, But should the adhesive prove difficult then remove the pushers/buttons.   cheers

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I seemed to like how light goes through the acrylic on my roommates watch. I have a watch that would look very interesting with acrylic too. Mineral doesn't do it justice.

The thing is, when I safely removed the crystal and its gasket, there is really no flat area where I can apply the glue on. The big flat area that you see is for the chapter ring, and not for the crystal.

I suppose a tension ring crystal might work in this case, but no place in my area has them. I cannot justify paying 25usd shipping for a 10usd crystal either.

Am I out of luck for doing it on this watch? What about acrylic crystals with straight walls?

20200226_121747.jpg

20200226_121219.jpg

20200226_121104.jpg

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Hi there, acrylic crystal with straight walls will work with uv glue or slightly bigger than the diameter of the opening. However you will lose any water resistance in that manner. But if you like the look of it then why not. Just remember to take it off before getting wet. On second thought I would go the slightly bigger method as the glue may end up on the chapter ring and you'll have to do it again. Use a crystal lift to put it on. Hope this helps and if you look around you can find thicker acrylic crystal for diver watches then you can glare at the crystal distortion from the side you will enjoy. That's a nice watch 

Edited by Graziano

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