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Author: Subject: DIY gasket for buchner funnels
alchemizt
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[*] posted on 7-3-2022 at 21:54
DIY gasket for buchner funnels


I have a buchner flask and a buchner funnel but cant find the rubber gasket anywhere so I decided to attempt to make my own. I got a tub of this liquid silicone that comes with a catalyst. How do I turn it into one of these gaskets:



I tried making a mold with tin foil but it didnt work very well. Has anyone here tried making one of these gaskets with silicone? Or has improvised a gasket in another way?
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wg48temp9
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[*] posted on 8-3-2022 at 00:10


When I have made a silicon gasket I used a polyethene sheet on the surfaces of the mold which can be peeled off the cured silicon easily. To hold the required gap between the surfaces of the mold I used suitable sized pieces of plastic in the gap. When the gasket is cured the piece of plastic can be removed and replaced with silicon rubber. I used this method to create a silicon rubber gasket on a gallon demijohn I had cut he base off to turn it in to a bell jar. The excess silicon squeezed out can be trimmed with a sharp knife when it is cured.

Silicon rubber bonds to clean aluminium foil but not polythene or the moisture cured silicon caulk I used behaved like that. I also let a slight skin form on the surface of the silicon rubber prior to assemble of the mold.

I suspect that hydrocarbon grease or silicon grease could be used a release agent but I have not tried that. Perhaps cling film could be used in place of polythene sheets as it would conform and stick to the mold easily.





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Sulaiman
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[*] posted on 8-3-2022 at 00:24


I cut a piece from a silicone rubber sheet, (about 1 to 2mm thick)
made a hole in it to fit the funnel, job done.
(you can seal to the taper as in your picture above,
or seal to the flat top of your filter flask)




CAUTION : Hobby Chemist, not Professional or even Amateur
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highpower48
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[*] posted on 8-3-2022 at 09:38


Should be able buy on Amazon. That's where I got my 2 sets less than $10.00 each.
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SWIM
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[*] posted on 8-3-2022 at 10:16


For my first adaptor on a Buchner funnel I just bored an appropriate sized hole in a large rubber stopper that fit the filter flask.






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alchemizt
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[*] posted on 8-3-2022 at 21:22


Quote: Originally posted by Sulaiman  
I cut a piece from a silicone rubber sheet, (about 1 to 2mm thick)
made a hole in it to fit the funnel, job done.
(you can seal to the taper as in your picture above,
or seal to the flat top of your filter flask)


Where do you get the silicone rubber sheet? Is there a way to reshape it so it completely takes the shape on the funnel?
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Antiswat
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[*] posted on 9-3-2022 at 15:30


if you need to make a hole in silicone rubber, redhot glowing steel will do, otherwise you might wanna opt for a metal pipe somehow adapted to a drill chuck, with the end of the pipe sharpened, i have used punches to drill clean holes through 20mm thick rubber before

as for making the fit... you just want to make like a small maybe 3mm thick sheet of silicone rubber, which should be well doable by just spreading the right caulk out on aluminium foil, or maybe even just the bottom of a steel pot, inverted then leaving it to dry- minding some caulk has concentrated acetic acid in it
then just cut it to size and make a hole fitting the funnel
i would say- im very happy for my 250mL flask fitting silicone plug
and, making one like that yourself shouldnt be super difficult, a large gluestick could make the hole that goes through the center
if you use aluminium foil to make a mold you can just carefully etch it away with an acid or hydroxide afterwards

infact- ... why dont you just smear a thick layer of caulk on the funnel itself? smoothen it out well with a wet finger before leaving it to set, if it peels off you should still be able to epoxy it back on, that would make for a very neat and effortless fit- im off to the patent office.




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