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.

<p>This is the best method for making o rings</p>
<p>Hunh...I never thought about doing this before! I would probably use the same PVC tube, slice it lengthwise and use it as a splint to hold the silicone together while it cures. GREAT idea you have there!</p>
<p>I love this@!@</p>
<p>Great instructable. I can't believe it hasn't been featured. Thanks for all the advice folks!</p>
<p>Hello everybody! Just an update... Recently I tried using a high temp red rtv silicone sold at most auto parts stores. Made some tubing that is much better than the silicone adhesive I was using before. Its oil resistant and heat resistant. It can withstand molten lead (smokes a little but it goes away) Motor oil and brake fluid didn't hurt it at all. Its far superior to the simple adhesive silicone which failed under high heat and most petroleum. It cost about 12 dollars for a regular caulking gun size tube. </p><p>I injected some into 5/8 clear vinyl tubing, then immediately used compressed air to blow out the silicone to make tubing. The length of the new tube will be about twice the length of the silicone sitting in the vinyl before its blown out.</p><p>Enjoy!</p>
<p>Here is a suggestion for getting more silicone into the tube. If you use a syringe on the other end of the tube to create a vacuum, when you go to push the silicone in the other end you it will help pull the silicone further into the tube. </p>
<p>Hell yes! Maybe an automotive vacuum pump, anything would help. Thanks for the idea!</p>
McMaster Carr (mcmaster.com) sells o ring cord stock (round, square, x-shape) by the foot (3 ft min) in 11 different materials (including silicone), 1/32&quot; to 1&quot; diameter, eight colors. For example, 1/8&quot; round black silicone stock is 84 cents per foot. <br>Could you use a short piece of tuning to glue the ends together in perfect alignment? Stick one end of cord in tube, apply silicone glue, stick other end of cord in other end of tube. Where cured, cut the tube away carefully. (I haven't tried it.)
<p>Good call! If joining two ends of tubing, that is the better way!</p>
<p>pretty damn cool</p>
<p>A pinch of salt to an old instructable: making a slanted joint increases the bonding area making it stronger, &amp; allows for a better fitting of the joint than a perpendicular cut. Saludos!</p>
Came here looking for a way to make custom sized o rings to seal a hookah I'm building. I plan on buying a length of silicone cord (I need to make a lot) but need a way to make it into a ring. This looks like a perfect method to join the ends together and very easy! Thank you so much!
Glad I could help! Enjoy that hookah! Love to see a pic...
<p>Not sure if I ever sent you what I made using your ideas but I did give you a shout-out in the video. Thanks again.</p><p>https://www.youtube.com/watch?v=OH0YQ125wpg</p>
<p>I'm so glad the gaskets worked out! If the gasket ever breaks, or if there is a defect, you could put it back in the mold and re-do the bad section. I noticed the the gasket picked up the red tint from the candle wax. Its a surprise sometimes as to what the silicone will do next to different substances (like acrylic paint or cornstarch) </p><p>Thanks for the shout-out! Love the truck too!</p>
<p>i also use this way to make an o ring</p>
<p>You could probably get away with moulding the O ring using a rolled up piece of paper coated in wax or PVA. because the tube looks difficult to get off. you can coat the tube with something i didnt check your guide. i would use a paper for making pvc cord and then join the 2 ends with something.</p>
Paper will work, ive used water to kinda dissolve the paper after the silicone cures. The silicone copies the texture of the paper giving a matte finish that looks nice. Wax paper works for for most silicone, automotive gasket silicone will stick to wax paper. Saran wrap or cling wrap also will not bond with silicone, used that for some neat looking shapes.<br>so much fun!
<p>Brilliant idea. Will the joint in these O-rings stand up to the pressure and pulling that might happen when the when they're placed between to parts that screw together? I need a large (~7&quot; diameter) O-ring for a cover that screws onto a container but I'm afraid that when I screw the cover on the O-ring might separate at the joint.</p>
<p>If you worry about an O-ring pinching or tearing you can add a little lubricant. The skin is important to it's integrity. So I could add that after removing from the vinyl tubing and gluing you should let it rest for awhile longer before using.</p>
<p>Thank you!</p><p>The joint if done correctly is just as strong as the o-ring itself. I have pulled some apart to test them, and they occasionally break at the seam, but only if there was an air bubble or some other defect there, and only when pulling pretty hard. I created these o-rings for a PVC tube submersible camera housing, and the o-ring sat between two surfaces: a PVC Pipe cap, and PVC coupler piece, and around PVC pipe. This sounds kinda like what you are doing. The o-ring can definitely withstand being twisted against two surfaces. I twisted the cap of this housing on as tight as I could. My Video camera survived 35 feet under water!</p><p>Good Luck</p><p> - Chris</p>
<p>Great. Thanks for the reply.</p>
<p>I liked this Instructable because it taught me and I enjoyed your fun in making something that might otherwise cost so much (because it has to be warehoused, entered to stock and marketed) that it is not feasible to build or repair an object that is worth far more than &lt;$1 glob of silicon sealant and a short amount of your time. Thank you. </p>
<p>I tried to blow the silicone out with 100 PSI but had no luck until I heated the tubing/silicone in very hot water. Then it worked well.</p>
<p>I made a mold for a silicone` O ring using a method I came across for molding chocolate! Put a flat layer of brown sugar (or cornstarch or icing sugar, apparently, but they're messy...) on a plate. Then carefully press whatever you're molding into the surface - I dipped in the top of the container I was trying to make a seal for. Then I used a syringe to lay down a small bead following the indentation. It would have worked better if I had a steadier hand and more experience with this kind of thing. The vinyl tubing might be more in line with my skill level, but I think it would be hard to produce a 1/16th inch O ring that way... (But if you can self-glue the silicone, I wonder if you could just lay down a straight bead and then join the ends...)</p>
You could just cut the tip of a syringe off to the diameter you want, and then extrude the silicone onto something that won't stick. You might have luck using water! Water will speed the cure and not deform the round profile of the oring. You could even manipulate the silicone into a straight line while it floats on the water.<br>Have fun!
<p>Oh, I hadn't thought of water, but that does sound like a fun experiment. I tried drawing a circle the right size and laying the silicone bead on wax paper taped on top of it, which was sort of cool and again would have worked better if I had a steadier hand. But in the end I laid a gasket on the inside of the lid of the container, and it didn't leak even after being submerged for several hours! (It's for a geocache...) I have a feeling it won't be a long term solution because the silicone doesn't stick to the plastic very well. More fun experimenting!</p>
To all commenters: just found a new way to rapid cure silicone! Acrylic paint. I just squeezed some silicone into a ziploc bag and then added few drops of colorful acrylic artist paint. I closed the bag and mixed up the ingredients. After a quick mixing I cut a corner off the bag and squeezed it out like a pastry bag. It changed the color of the silicone obviously, and it starts curing almost instantly so don't waste any time. In fifteen minutes my blue silicone chunk was completely cured. And it seems to actually be stronger than bare silicone... Maybe the acrylic polymer strengthened it? <br>It didn't take much acrylic paint to set the rapid cure, prob only needs a few drops per golf ball size blob.<br>You gotta try this!<br><br>Chris
<p>Great instructable. I used a 1/4&quot; OD tube to create an o-ring for a leaky OtterBox pursuit 20 case after I already voided the warranty. A bit of silicone lube from Ikelite helps it to slide right into the groove.</p>
Man that's great! Thanks for the comment!
Heat will speed up the curing time... carefully...
If you want to speed up the drying time, mix about 2 parts silicone, 1 part cornstarch, and (if you want to, you don't need to), 1 part mineral spirits. The drying time will drop to ~ 1/2 an hour for any thickness even several inches.
Thanks for the comment! Another maker suggested the corn starch, which works great, I will try the mineral spirits next...never thought of using that since it works for cleaning up. Side note; silicone cured with corn starch is irresistible to roaches. Its not like there's better stuff to eat in my workshop, but they go for the silicone anyway.
JAJAJAJAJAJAJAJJA... REALLY ??? <br> <br>are you for real? jajajajajajajaj.... so, it could be something to use to trap them?
Personally, I've never had a problem with that, or any bugs eating my molds.
I'll find the way to use that knowledge on some instructable...
This is a fantastic instructable! *favorites it imediatly* <br>I had no idea silicon made such a great seal <br>I can finally start making an HHO welding torch!
Could you inject a little at a time say an inch, let it cure blow it through a bit and then inject more building up the length required gradually.? Would this solve the long cure time for larger diameters? Thoughts? <br>
That is not a bad idea, and pushing the wet silicone through the vynil while it is plugged with a cured section should not be a problem, escaping air should get by. Only problem might be getting new silicone to mate with the old without any air pockets.<br>Where did you find o-ring cord? :-) <br><br>P.s. I bailed on making any more camera housings, go-pro makes my hobby obsolete!
Also you can buy o-ring cord in various diameters from 1-10mm in lengths of 1metre up. I presume you can still use the method shown to form the cord into a ring.
This is excellent! I didn't realize that silicone caulking would make such an excellent gasket. It seems like it would take a really long time for the silicone to cure in the tubing though, considering it doesn't cure in the original dispenser... <br>How fragile is the resulting product? <br>My housing is basically two pieces of acrylic. A 1 inch piece of acrylic with a hole routed out in the shape of my camera, and a second 1/4&quot; piece of acrylic as the front plate. My plan was to buy some neoprene gasket sheet to seal the gap between the two pieces of acrylic, but after seeing this I am thinking it might work better just to route out a groove in the 1&quot; piece of acrylic and over fill it with silicone caulking. Do you think this will work?
Your idea will definitely work. The silicone still might take a long time to cure, I believe the acrylic will not breathe at all like the vinyl does. The silicone should not stick at all to the acrylic when cured, so your gasket will be a perfectly formed to the routed channel. I would leave a gap between the sheets of acrylic so that the silicone has access to air for the curing, and so the outer acrylic pane has room to compress the silicone when it's under water. <br> <br>I would love to see a picture! <br> <br>Thanks
P.S. - the silicone is not fragile, it is very forgiving!
Would it be possible to extend your procedure to make optical fibre ? <br>Crystal clear silicone and teflon tape on the outside should work .. <br>
you can add corn starch, like in mike77's instructable, it will speed up the cure time dramatically. here is the link to it http://www.instructables.com/id/How-To-Make-Your-Own-Sugru-Substitute/
it sounds good, but how do you get it in the tube after it's mixed? I really want to try this
I have since tried mixing the corn starch with silicone, and it does cure much faster, however there seems to be some weakening of the material. It doesnt stretch as much. If I were going to mix starch with silicone to use in o-rings, i would use an empty caulking gun tube: mix the starch and silicone very fast, and spoon it into the empty tube, put the piston thing in and then fill the vinyl tubing. <br>Also, roaches like to eat silicone cured with corn starch!

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