# how to fold a filter paper to use in a buchner funnel?



## ericrm (Aug 4, 2013)

does anyone has some good technic on folding filter paper to allow use with a buchner funnel (using a paper too big) so the side goes up the top side of the funnel. i manage to get the side round enuf but as soon as i put liquid in it ,it deform and allow air to pass on the side...
any idea would be welcomed


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## rickbb (Aug 4, 2013)

Cut it round so it fits flat on the bottom covering all the holes. Spray with distilled water to wet it and make it stick to the bottom and create some vacuum before you start the pour.


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## ericrm (Aug 4, 2013)

thank you Rickbb i appreciate the help but your missing the point ,i have the correct sized filter paper , but i have also some bigger filter paper that, if possible, i want to fit in to take advantage of the excess paper so i can make sure that the material doesnt stick on the ceramic funnel side. i will have to filter pm, than incinerate the filter, so i wish to minimize the amount of filter paper.


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## Smack (Aug 4, 2013)

Very little fluid will pass through the paper beyond the holes, so having a over sized paper won't do anything the proper size can't do. I always use two papers when filtering for two reasons: 1 I use one fine or slow paper on the bottom and a courser one on top as a pre-filter. 2 Having two in the funnel helps to keep me from over doing the vacuum and blowing a hole in the paper.


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## chlaurite (Aug 4, 2013)

The same idea works, even with "real" filter papers - You can just cut bigger circles down into smaller circles, same way you would with a coffee filter. You don't need to bother with the 2-way fold to make the "pocket" when using a Buchner.

I find it helpful to find something round that <I>just</I> fits inside the funnel, and use that to trace out your circle before cutting. But you could free-hand it if you have a good eye.

Smack - Funny thing, I use a slow and a fast too, but in the opposite order (on the theory that it lets the top paper use more surface area for filtering, rather than just getting little black dots over the holes). I'll have to try your way next time and see which works better, makes a lot of sense! :idea:


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## mjgraham (Aug 4, 2013)

I normally have to use two papers also , I don't know how many time right at the end it sucks a hole in it is ruins all the work. When I want to keep stuff off the sides I'll put a filter disc in the bottom and use a coffee filter on that. As for folding a over sized paper I am not sure unless it was way over sized when it is submerged in liquid there won't be any pressure to hold it on the sides (liquid on both sides, no vacuum on the cylinder part) so it will float loose, my theory anyway may be wrong on that.


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## ericrm (Aug 4, 2013)

Smack said:


> I always use two papers when filtering for two reasons: 1 I use one fine or slow paper on the bottom and a courser one on top as a pre-filter.


i tought about it but never tryed it , did you see a big amelioration on gelatineous and fast clogging filtrate?


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## Smack (Aug 5, 2013)

Like a solution with tin in it, it helped a bit, probably doubled what I could do before not being able to get any fluid through. Tin will settle out after a day or two then you can siphon off the clean solution and filter that and process the stuff that settled separately instead of trying to filter a poor solution like you mentioned. Just mentioned tin not knowing what you have because that's usually what people have trouble with.


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## ericrm (Aug 5, 2013)

i was thinking about hydroxide but is a similar problem as tin... 2time longuer is still better than regular filtering ,thanks for the tip


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