Superlative oil filled F-91WThe Making Of; the Superlative Oil filled Casio F-91

[HomoCaballus]

    The Making  Of; the Superlative Oil filled Casio F-91W DeepSea

The humble  yet iconic Casio F-91W is a pretty good watch and costing only some 12 euros it  is just about impossible to beat its value for money. Small wonder it is the  world´s most worn wristwatch by far.
It does  have two weaker points:
 

• the strap, which is prone to       break over tome
• the water resistance, which is       only shower proof

     
The first  issue is easily enough solved using G-shock strap adaptors so it can be used on  a ´Nato´ type woven strap.This way  mounted on the strap the head does not get stressed when there is a pull on the  strap and the strap itself is unbreakable.
 
The water  resistance is a more challenging issue. There is  however a solution which is as effective as simple to apply; fill the head with  liquid to start with.
Since a  liquid cannot be compressed simply filling the watch with liquid without any  bubbles would fill it at zero pressure meaning the liquid will stay in as the  seals can take thát.
Since a  liquid cannot be compressed simply filling the watch with liquid would make the  watch resistant to any further liquid ingress to whatever depth since it  already ís 100% full.
 
Ok. So what  liquid to use?
Oil is the  simplest since it does not conduct low voltage currents and is water repellant. 
Vegetable  oil would be compatible with rubber and plastics.
Since the  F-91W is thé campo watch worn by just about áll   workers in the olive oil industry and extra virgin olive oil is the  superlative vegetable oil, the choice was made; extra virgin olive oil.
 
A first  test revealed that the quartz module would submersed in oil indeed keep  funcioning as Casio intended.
It also  proved to be a bit of a pain to fill it for 100%;.
The idea  however proved sound as lowering into a two metres deep tank gave no problems.
 
Time to do  it properly:
 
Step  1.  prepare everything needed 

 

Step 2.  once prepared with a bocadillo seranito and a nice glass of Tempranillo, fill  the bowl and remove the case back



Step 3.  lower the head into the oil, with one side down and sssssslooooooowly inmersing  it to give all the air time to rise and exit




Step 4.  lower the case back, inner side up and while inmersed turn it round and put it  on the back of the head, taking care not to trap any air




Step  5.  put the screws back while retaining  the oil




Step 6.  check



Step 7.  clean the watch and enjoy the Superlative oil filled F-91W


 

Using this olive oil has the additional advantage that the greenish colour cléarly shows that the watch is filled with it.



HC


p.s. I forgot     to mention:
Because there is now no air inside, there is no refraction on the inside of the ´crystal´, so the legibility under the slightest angle has been noticeably improved. It is like the inside has the ultimate AR coating.

[rileynp]

HC,
I took the liberty of embedding your photos- band-width isn't a concern when such pioneering horology is going on, but thanks for being mindful.  I remember before I really got into watches I was taken by the idea of filling a watch with oil for water resistance (before I knew there were companies that did so), and the idea is still captivating even now, especially in such a DIY way.  I will be interested to hear how well the watch contains the oil over time, do keep us informed of any changes- science depends on it!  Thanks for sharing, sincerely.

[JohnN]

that is just flat-out amazing!   

[LUW]

You filled your watch with olive oil. Extra virgin olive oil.
I don't know if I use this smiley or this one .

[sharkfinDave]

Now that is just crazy cool. 
Love the hydro watches. I remember somebody over in the gshock forums did this too.
Great pictorial for your endeavor. EVOO, healthy tasty choice. lol.
I've read that olive oil can go rancid over time. But being sealed and all, wonder if anything would change.
I guess changing the battery would just be another go at this same process you just did.
Keep us updated. I'm tempted to try this on my Mudman.


Cheers, Dave.

[kai_h]

I would have used mineral oil personally but I love the green tinge from the extra virgin! 

[HomoCaballus]

Thank you guys.

As for the oil retaining it is important to get all the air out and not to overfill. Since the plastic case is flexible you can fill it to the point of bulging. When the thing warms up this will put a lot of pressure on the not so seals.
The trick is to press the middel of the caseback firmly down so you will squish the oil out.
It also helps to use temperate oil.

Do NOT use mineral oil nor anything synthetic!!! There is no way of knowing wether it is compatible with the rubbers and plastics.
I use olive oil because it is visible.  I have appropriate silicon oil on the shelf but that is invisible, so nobody would believe.

Although I knéw what I was doing it remains a véry strange to experience that the light is working 

I have read a lot of crap about liquid filling in pressurised sealed chambers and wr ratings and this is a nice relativating illustration 


Bottom line however is that the F-91W now has an indestructable strap and unlimited WR rating but the best thing is that it is huge fun, functional at the price of beer money 

[ADB]

A very original mod, but it does make changing the battery a bit messy.
Also the reason oil-filled commercial watches are filled with special mineral oils is that organic oils degrade (oxygen and bacteria) with time, they become acid and this will inevitably compromise the rubber gaskets. In your case the worst that will result is an oily wrist and a loss of a few dollars, but on a $1000 or more diver's watch under warranty, it's an absolute no-no for the manufacturer.
Here is a page with several silicon oil filled G-Shocks: http://mygshock.com/2008/10/13/g-shock-hydro-conversion-pressure-test-2/
Cheers,

[LUW]

And what about using liquid silicone? That wouldn't harm any plastic or rubber.

[HomoCaballus]

A very original mod, but it does make changing the battery a bit messy.
Also the reason oil-filled commercial watches are filled with special mineral   oils is that organic oils degrade (oxygen and bacteria) with time, they   become acid and this will inevitably compromise the rubber gaskets. In   your case the worst that will result is an oily wrist and a loss of a   few dollars, but on a $1000 or more diver's watch under warranty, it's   an absolute no-no for the manufacturer.
Cheers,

 
  Low acidity is the criterium for ´virgin´ and more virgin than virgin less acid still 
 
  EVOO is renowned for resistance to oxidation but that is not important since the stuff is sealed air tight without air.
  To make sure it started fresh I opened a can straight from the press down the road 
 
 
  A battery change is a once in 7 year operation and would simply   incorporate an oil change. No, not more messy than the original filling   which was not messy.
  Remember it is vary tasty and nice smelling oil. The bocaldillo   serranito and tempranillo were in the first picture for a reason.
  Combine it with lunch!!!!
  All you need is a chunk of bread, a piece of cheese to clean up.
 
  Oh, and you know those vanilla scented rubber straps? My watch now has the rich bouquet of quality EVOO 
 
 
  Anyway, bottom line is that my F-91W ís more functional now but   foremostly this topic is about having fun with watches and relativating   the part of wisdom taking itself and the whole thing too seriously.
  So, mod your´s tomorrow while enjoying a nice meditaerranean sunday lunch   

[HomoCaballus]

And what about using liquid silicone? That wouldn't harm any plastic or rubber.

As I wrote, I have that on the shelf but it is crystal clear, so invisible whereas I wánted the greenish hue to advertise ´EVOO Inside´ 
Also it does not make for an enjoyable lunch and is not nice smelling.

[LUW]

Well, that's the first salad watch I ever saw .

[ADB]

  ...
The bocadillo   serranito and tempranillo were in the first picture for a reason.
...
So, mod your´s tomorrow while enjoying a nice meditaerranean sunday lunch   

I must say your bocadillo made me hungry! 
Cheers,

[TheTigerUK]

A really "fun" post and very interesting, well in a way sort of amazing and no chance of corrosion i should imagine and does/would it improve water resistance ?

ps: Your lunch does look appetising

[Time]

that's pretty impressive.

[HomoCaballus]

that's pretty impressive.

Well, thank you.

It was intended as both fun ánd solve two ´problems´.
Between brackets because a DW5600 is cheap enough more capables till, but that would not have been zero fun.

Now imagine the same sort of thinking&doing applied to a turbo diesel with in-line pump engined offroad car 

[HomoCaballus]

Pressing the wrong button I got a search on TheWatchSite instead of going there.

Boy, was I laughing when I saw what the third hit is....

It is still going strong btw. I have hardly worn it as the SDGA has been/is the daily beater but it was only a few seconds off when I set the DST and there is no sweat or what.

[mwbuss8]

I'm working on trying this with an analog watch which has other complications. I have a very thin silicone oil I'm going to use. You mentioned that you like the bit of color the olive oil adds though. This got me thinking, what about DOT5 brake fluid? It is a silicone oil, it is dielectric, and it has a faint blue tint. Has anyone heard of this being used?