my understanding of the use of silicone (@Archer) is not for water resistance per se but to allow the caseback to be tightened down without pinching or pulling, I assume it works the same with gaskets in the crown or tube

 

Yes applying silicone grease is the standard way to keep seals watertight

my understanding is that the grease helps prevent the seals from cracking, tearing, and otherwise disintegrating; which might happen when they’re dry and under pressure

 

Yes, silicone grease on a Vostok crown.

 

Good responses everyone.

 

I realize that silicone is used to lubricate caseback gaskets. In addition to the lubrication it would help prevent the ingress of water.

Does anyone use a tiny amount of silicone on the o’rings or gaskets in the crown or crown tube?

Yes, silicone grease is used on the crown/case tube as well as the case back gasket. It's used on pusher gaskets also.

It's a lubricant that prevents stretching, wear, and cracking of seals. It doesn't do any sealing itself - so if you have a watch that is leaking past the seals, you can't just add some silicone grease to make it water resistant again.

 

And it's so inexpensive, why not take care of your investments. The slippery stuff keeps the rubber supple and aids in the tightening and loosening of the threads on your crown. The reason it's used on screw down case backs is so the rubber won't bind up in the groove. On the crown it helps the stem slip inside the seals making it smoother to wind and set the hands and date complications.

And as was mentioned, this is grease, not a silicone sealant. It doesn't dry up to create a seal. The rubber gaskets do that job.

 

Thanks to all for the comments and the insights. Very much appreciated!

There is a chance that silicone grease also helps provide some additional water resistance. Here’s what I know without making the story too long.

After I graduated, my first job was doing electrical logging of oil and gas exploration wells with Schlumberger. Long tubes made of solid titanium held different types of electronics. (Schlumberger joked that outside of the aircraft industry they were the highest users of titanium) There was a large ‘connector’ that went from the armoured cable that shielded the wires and slid over the titanium tool. The cable and its supply on a huge drum allowed the tool to go 10,000+ feet into the well.

The tool had two spaced circular grooves to hold 2 o’rings. The o’rings had to be changed with new ones before any run into a well. The o’rings were about 1/4” thick and 3” in diameter. It was vital that the o’rings, grooves, and surrounding metal had to be slathered in silicone grease. We literally went through tubs of silicone. The connector was then slid over end of the tool and screwed securely in place.

During our training classes, experienced field engineers explained about the incredible downhole pressures and temperatures in a well. Any fluid under high pressure would push against the silicone and any imperfections in the o’rings. The silicone would ‘fill’ the imperfection(s) first and maintain a 100% high pressure seal.

The term imperfection is very broad. It is not necessarily a defect in the o’ring or the groove itself, but could it could be in the seating of the ring, or the pressure agent causing a breach in the seating and resulting in ‘flooding’. While silly, you could think of silicone as being the ‘finger in the dike’.

There were many times I unscrewed a connector, carefully slid it back, and saw pristine silicone grease, 2 clean o’rings, a bit more grease and then a sleeve of brown ‘mud’ that was waiting to get in. While called mud by the industry, it is actually quite a complex and multi-functional drilling fluid. There are other nasties downhole that do not coexist nicely with electronics.

Ever since, I have always used plumbers silicone grease for any installs/repairs involving o’rings or rubber gaskets. Guess what? I slather. (big box hardware stores carry small 1” tubs of high quality silicone grease. Grease ... not adhesive, lol)

My apologies for the lengthy saga and hope it adds to understandings.


Sent from my iPad using Tapatalk

 

I have never found that adding silicone grease (or using more grease) has allowed a watch to pass pressure testing, that otherwise would not pass. Also, there hare many instances where O-rings are not lubricated with silicone grease, and the watches pass pressure testing just fine.

The silicone would ‘fill’ the imperfection(s) first and maintain a 100% high pressure seal.

On the surface this seems like a very misunderstood explanation, or someone was pulling your leg (something every new engineer experiences, at least I did many decades ago). If there are imperfections that would otherwise let water and mud through them, then why don't the high pressures push the silicone grease through those same imperfections, with water and mud quickly flowing behind the grease? Somehow the silicone just magically stops after it has filled the imperfections? That just doesn't make sense.

Certainly in a threaded connection like you describe you want to liberally slather the O-rings in grease, because that will prevent them from bunching up as the connection is threaded together. It allows the surfaces to slide over the seals, and not grab them, which can lead to stretching them out of shape, compromising the seal. This is the same reason you use it on a threaded case back O-ring. Not because it will fill imperfections under pressure, because watches are not just tested under pressure, but also under vacuum.

Cheers, Al

 

In my experience, silicone grease is part of the water resistance "system".
It lubricates and helps prevents deformation, but it also adheres to the o-ring and the faces of the parts joined. A coupling depending upon o-rings for gas or liquid tight sealing, may not be impervious to gas/liquids without silicone grease, but is rendered effective with the grease. It definitely adds to the water resistance since it adheres and does not mix with water...(similar to joint compound for tapered pipe threads)...fills in the gaps, sticks, and is resistance to water, oil and gas.

However, as Archer said above...it is not a cure for defective o-rings or joint faces.

Regards, BG