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Way to seal glass to brass?

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  • Way to seal glass to brass?

    Hi folks, am making yet another specialty tool that is requiring me to seal a 6mm lab test tube to a brass adapter. The adapter is just going to have a hole in it with no mechanical way of fastening the test tube, so I need a chemical way. This is a site glass gauge for adjusting carburators and will be subject to direct contact with gasoline.

    Any suggestions?

    Many thanks, Derek

  • #2
    There is a Loctite product designed for metal to glass bonding. I just do not know if it is resistant to gasoline.

    I recommend contacting reps for Loctite, Gorilla Glue, and 3M to see what they have available.


    • #3
      Thank you. The datasheet says it has chemical resistance to petrol. Will contact them to verify. I appreciate the pointer.



      • #4
        Is this a one-off run or for production? You could use one of the Phenol Novolac Epoxies. These epoxies are gas, oil and solvent resistant.
        If you're going to make a lot of them, use one of the fuel tank sealers such as this: PN Epoxy.


        • #5
          Originally posted by CCWKen View Post
          Is this a one-off run or for production? You could use one of the Phenol Novolac Epoxies. These epoxies are gas, oil and solvent resistant.
          If you're going to make a lot of them, use one of the fuel tank sealers such as this: PN Epoxy.
          1-off run. Just going to make 1 or 2 for carburator pairs, then loan them out to folks with similar setups. Will ask my local radiator shop if I can get a small batch from them.

          Thanks, Derek


          • #6
            Please show us the finished product!


            • #7
              Isothalic resin is supposed to be fuel-proof. You might visit a boat builder who also works with fuel tanks- they might be able to give you a small quantity. You could mix it with some powdered glass to thicken it into a paste. Of course you'll need some catalyst.

              Might be better to look into the various epoxies. I don't know if PC-7 is fuel-proof, but I do know that one of the products that used to be called SuperMend is. I think one company now handles the SuperMend line and PC-7. Heck, maybe JB weld would be fuel-proof, but you have probably thought of that already.

              Ok, I just looked it up- PC-7 demonstrates excellent resistance to bla bla, gasoline, fuels, bla bla
              Last edited by darryl; 05-07-2013, 12:00 AM.
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


              • #8
                High density polyethylene works well as a seal for gasoline and also can be melted like wax to flow a joint. I would wrap the brass around the glass, sleeve the brass with HDPE and heat the assembly to flow the HDPE in the joint. When it cools, the HDPE forms a seal and the brass shrinks more than the glass. Use borosilicate glass test tubes (Pyrex) for heat resistance to make a more stable product.


                • #9
                  Greetings derekg !

                  You can buy glass to metal seals. I've used them extensively in my work over the years. We get ours from Varian but there are many other companies which offer them. Here is a website showing some products. Check the links at the bottom right of the page as well.



                  • #10
                    At first I thought brazing. But I doubt it would stick... Also the temps are a little extream.

                    What about sodium silicate? I would think it would be gasoline resistant once set and seems to have been used to seal exhaust systems and cement things to brass.
                    Not sure how well it will stick to glass, mind you.. But I would think some frosting/etching/sandblasting of the glass would seriously help with whatever adheasive you use.

                    I'll have to remember that HDPE trick!
                    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


                    • #11
                      Originally posted by derekg View Post
                      no mechanical way of fastening the test tube
                      No chance of an o-ring or two?


                      • #12
                        There is a product that has been used for sealing gas tanks since I was a kid. It's called Seal-All and is available in any hardware store. It works on plastic poly gas tanks, metal tanks, etc.

                        It isn't a fancy epoxy or anything, but it works quite well.

                        Regarding mechanical retention, never underestimate what you can do with stainless steel aircraft wire typically for retaining fasteners. You could easily 'weave' a simple net around the tube to mechanically retain it.


                        • #13
                          I think epoxy or machining an O-ring seal are probably the best ways to do this. However if you're looking for something exotic you could go with indium metal. Indium will stick to clean glass and brass no problem. RotoMetals sells indium.
                          My cup 'o plasma: No dialog, just ten minutes of dancing plasma and music. Turn on, tune in, space out.


                          • #14
                            Where I was going with the o-ring idea is o-rings are great at gas sealing but miserable mechanical strength, but epoxy is not so great at gas tight seals, but really strong if done right, so a mix of the two... an o-ring to keep the gas in the tube, and the epoxy to mechanically stabilize the o-ring...


                            • #15
                              Sika has a product made specifically for bonding glass to metal. Sikaflex 295 adhesive
                              It is used in the marine industry for bonding glass to fiberglass, aluminum
                              I suspect that once it is cured gas won't bother it but you can check with them at < >