Homemade Silicone O-rings and Tubing

Intro: Homemade Silicone O-rings and Tubing

Make your own O-rings and tubing from silicone!
The object in this picture is a homemade submersible camera housing, made possible by the silicone O-rings.  (my next instructable will be the camera housing)

Quick and dirty explanation: Inject silicone adhesive straight from the tube with a caulking gun into clear Vinyl tubing, let it cure, blow the silicone out with compressed air, cut the silicone to length, re-glue it to form rings. If you want tubing, blow out the silicone before it cures...
This instructable will not only show how to make the O-rings and tubing, but go into detail about the way silicone adhesive behaves so you can exploit it, and make even more things!

STEP 1: Materials

The primary material is Silicone adhesive that comes in tubes for caulking guns.

1. THERE IS A DIFFERENCE AMONG SILICONE TYPES. DO NOT USE "Silicone II", it is not pure Silicone, and will not behave as predictably as "Silicone I" , (or 100% silicone). The black Silicone is from ACE and is my favorite. Clear GE Silicone 1 is great too.

2. Clear Vinyl tubing. This is what you will be pumping the silicone into, it's the mold for the O-ring and tubing. The "I.D." or inside diameter of the tubing will be the "O.D." of the Silicone O-ring you are making.

3. Masking tape, compressed air, sharp knife, high quality caulking gun, about a week of cure time.

STEP 2: Inject the Silicone Into the Vinyl Tubing

Using the caulking gun to force the Silicone into the Vinyl tubing, squeeze away! You will notice that as the Vinyl tubing fills up with silicone, it will get harder and harder to fill, due to the high viscosity of the Silicone. It will take considerable pressure to hold the Vinyl tubing onto the tip of the caulking tube. (a nice caulking gun is worth the price here)
You may only be able to pump about 15 or so inches of silicone into the Vinyl before it just wont take anymore, and you will actually feel the Vinyl tubing expand from the pressure!

The tubing shown here has an I.D. of 1/4 inch, which is an amazingly convenient size. The only other size of tubing I've tried is 1/8 inch I.D., anything bigger than 1/4 inch I.D. will take some special care... but more about that in a minute.

STEP 3: Optional : Make Hollow Tubing Instead of Solid Silicone

At this point the Vinyl tubing is filled with uncured Silicone, and you can keep it solid, or make tubing out of the silicone itself!
All that needs to be done is apply compressed air back into the Vinyl tubing, which will force the uncured Silicone to flow back out, while leaving enough of it stuck to the inside of the Vinyl, so that when it cures, it will be tubing!

If you use compressed air to do this, use the bare minimum amount of pressure. The reason is, after the silicone is forced out, the sudden blast of compressed air through the tubing will cause the thin film of uncured silicone stuck to the inside of the Vinyl to "Ripple" due to violent turbulence of the compressed air

STEP 4: Waiting for the Silicone to Cure

Now comes the waiting... a little extra information while we wait for the cure:
The interesting thing about this method, is that the Vinyl tubing material, though waterproof and highly resilient, will not prevent the Silicone within from curing. The Vinyl does not make a good "vapor barrier" and therefore permits curing. Silicone cures from the outside in.
The (solid) Silicone if left in the 1/4" Vinyl tubing may take more than a week to cure. If anyone has ideas on how to speed up the cure< let me know.

The silicone that has been blown through to make hollow tubing, will take a single overnight, maybe more.
The difference is that the air can get to the inside of the tubing and help it cure faster.

Being the impatient person that I am, waiting is hard. The first few times I made these, I kept checking and checking. The Silicone that is near the ends of the Vinyl tubing will cure relatively quickly, even up to a half an inch of it will quickly cure due to its proximity to open air. Do not be fooled, the Silicone deep inside the Vinyl has a way to go yet.

You may want to make a few lengths of this tubing at once, if for no other reason that to test how the cure is coming along. Just cut a section of your test tubing, any others should be about the same.

If anyone uses Vinyl of more than 1/4 inch I.D.  Let me know how it goes!!! (my prediction is a ridiculously long cure time...)

STEP 5: De-molding the Silicone From the Vynil

Now comes the really really fun part! - Removing the cured Silicone from the Vinyl tubing!
There are two methods for doing this. The compressed air method works only on solid Silicone. It's as simple as it looks: Hook compressed air up to the Vinyl tubing and blow!
This method at first seems like it wouldn't work, after all, you cant push on a rope right? But what happens, is that the compressed air will cause the Vinyl to expand, and therefore separate from the cured Silicone within, leaving a slight gap... the compressed air will work it's way down the gap between the Silicone and the Vinyl, and create turbulence between them.

The sound of this happening is hard to describe, but sounds like pinching a latex balloon opening so that it squeaks loudly. The Silicone will shimmy its way out of the Vinyl without you having to do much except laugh at the simplicity of it all.
(This joy is similar to the joy experienced by the Flying Spaghetti Monster as it gives birth to spaghetti children... or so goes the legend anyway)

If your Silicone is still uncured, this whole thing will not work.

The second method of Silicone removal is to simply pull it out of the Vinyl by hand. Since the Silicone shrinks when you pull a piece of it length-wise, it will pull away from the inside wall of the Vinyl tubing, and come out. You will probably find other ways of doing this, i.e. with water, etc. If you use the "pull method" it helps to straighten out the Vinyl tubing.

STEP 6: Cutting the O-rings to Size

From the Silicone that has emerged from the Vinyl, you now have material for your O-rings!

1.Cut the Silicone rubber "cord" to the desired size (circumference)
2. Make the cut ends as flat and uniform as possible.

The silicone "cord" is VERY flexible and soft: pre-stretching it (by making the O-ring slightly small) is very usefull here, if your O-ring is meant to hold snugly around something. The Silicone should stay soft and pliable for a looooong time, many years.

STEP 7: Join the Ends to Make the Final O-ring

Basically, you're going to use the same Silicone adhesive that you made the O-rings with, to glue the ends together.

1. Using masking tape, wrap both ends of the cord. Doing this prevents the Silicone you use for the fusion, from getting onto the smooth surface of the O-ring.

2. Using a wider piece of tape as a cradle, position one end of the O-ring.

3. Glob some Silicone onto the other end of the cord

4. Push the ends together, then lock the tape down. There is actually just a tiny amount of silicone used to fuse the ends together!

5. Keep the taped ends Parallel to each other, the O-ring will be "round" don't worry!

6. Wait overnight for cure

STEP 8: Remove Tape, You're Done!

Remove the tape, and clean up the extra silicone from the joint, which should be very easy, since the tape prevented the silicone at the joint from sticking to the O-ring. The joint will leave a little imperfection in the O-ring, but the Silicone is so pliable, it will not affect sealing performance.

Enjoy, and good luck!

(My next instructible will be how to make the submersible camera housing!)

Comments

[noobyme]

Hey what do you think of using 3d printer filament as o ring? No printing it, just the filament itself you can fuse one end to the other with heat

[CaptainChrisso]

Hey there Noobyme, I havent got onboard the 3d printing train yet so I can't say for sure. If they make a softer filament then it would probably work. In fact they should make soft rubber or plastic filament so we can make all kinds of gaskets and seals!

[noobyme]

They do make TPU and TPE. 95A. Just a thought

[owlclicks]

Well, little old me knows the best way to cure the silicon faster! I made a few lengths of silicon tubing yesterday afternoon and stuck it in a vacuum chamber at 4psi that evening. This morning its completely solid!

[CaptainChrisso]

Thanks Owlclicks! My understanding is that the humidity in the air is what cures the silicone. Ive been adding acrylic paint to silicone, and not only does it tint the silicone, it cures it really fast, with only about 5 minutes of working time. But now you've got me thinking that silicone under a very good vacuum wont cure... which might help in preserving my unused silicone...in any case Im gonna get a vacuum pump and start experimenting. I hope your silicone tubing turned out great, best of luck with your projects!

chris

[MaddyG1]

Thanks so much for this clear and humorous explanation. I just wanted to join my silicone tubing for making necklaces. I appreciate all the photos.

[CaptainChrisso]

Thanks for the comment Maddy! I'm so glad you enjoyed it!

[MarcS16]

Ok so I am filling a 7/8” id tube. It’s not a vinyl tubing because of course they don’t have that size immediately available anywhere, of course because if I want it then they don’t have it usually is how it goes, so I am using acrylic plastic for now, at least it’s 7/8” id.

My question is does the nozzle of the caulk tube have to be air tight inside the tube? Or do you simply just stick it in, squeeze and fill it up?

[CaptainChrisso]

Hello, Just found your comment today, so sorry If I'm late!
YES! The nozzle needs to be airtight against the id, and you will have to create an adapter to make this happen I would suggest wrapping the silicone nozzle with electrical tape to increase its od. I'm guessing the cure time will be over a week. As for getting the silicone out, maybe put a blob of silicone on that sticks out from the tubing, that you can later cut off.
Let me know how it goes!

[MarcS16]

So if we were to say pull it out by first stretching out the ends, how do we grab the ends if they are inside the tube? Breaking or tearing a little of the tube on the ends would have to be done to get a better grip.

[bushnell1karl]

Try imersing in a bath of water..?

[Leo Viet]

Have you tried it? Does it work?

[Mark_In_Brazil]

Hello
I am trying to stop this 10 liter ceramic water filter from leaking. It has two pieces ( upper that houses the filters and lower that houses the filtered water ) and leaks where the two meet. I am going to try to put a layer of silicone on each of the mating surfaces, letting it cure and then put a small bead of silicone in between them before I mate them together. My question is; do I need to put some sort of lubricant on the ceramic before the silicone so it will not adhere to the ceramic?

[CaptainChrisso]

hello! cool rig you have there! i believe the silicone will stick very well to the ceramic, so something will need to be put on the ceramic to act as a mold release. wax will work very well for this, and wont make a mess, or contaminate the water. i would use canning wax, if you can get it, its just clean candle type wax,or paraffin. rub it on the ceramic like waxing a surfboard until its very well covered. buff the wax to smooth out bumps and stuff. cure the silicone for a couple days to make sure any thick silicone has enough time.
good luck!

[Mark_In_Brazil]

Thank you kindly for the response. Had not crossed my mind to use a wax base. Makes sense. I will certainly give it a go!

Thanks again

[Insomnus]

You have made my day! I was looking for a tube of a certain size and shape - now I can make my own, thank you.

One more detail: The FSM gives birth to spaghetti? Is his almighty Noodleness a female? Who's yer daddy? Many, many years ago I saw a documentary showing the Spaghetti harvest in Italy. Oh - I found it on YouTube, it was made in 1957 (which shows how old I am).

[CaptainChrisso]

I made this instructable back in 2010, and I didnt see your comment until just now. Had a hearty laugh at the spaghetti video. Wish I could have seen it sooner!

[katou]

Had some nylon tubing, gave that a go. I was worried it wouldn't let any water vapor through and thereby fail to cure.

Hoping that they were similar, I decided to compare the vapour permeability for vinyl tubing and nylon.

Vinyl tubing (actually PVC)
33 g/m2 over 24 hrs

Nylon tubing
270 g/m2 over 24 hrs

Looks like I can relax!

Nylon tubing is used to hook up refrigerator ice makers in Canada and the US. It is usually a translucent, milky white and much stiffer than same size vinyl tubing.

Katou

[CaptainChrisso]

Thanks for the comment! I concur with the icemaker tubing. I tried to go large with PEX tubing, and the silicone bonded to it permanently, LOL, however it did cure solid to my surprise.
Im curious to know your method for measuring the vapor permeability, and what your measurements mean, I would love to know more about the chemistry too.

Thanks!

Chris

[offtherails2010]

ugh sorry for the repeat postings, dont know why my computer isnt saving my text, showed up as nothing written when i reloaded page then typed everything again.. ugh