Has anybody had problems with filter paper that just won't sit flat in the funnel no matter what! I have various haldenwangers and many different grades of paper (many of then are old, bought from auctions), but the only stuff that I can get to sit flat without creasing it are the glass fiber ones.

Can older papers distort with time?

Thanks,
FF

Wet the paper with the solvent you are going to filter, and it will soften and fit much better.

are you vacume filtering? if so it should stick very well. when it is wet.

Yes vacuum. Wetting, pressing, yelling, they just won't sit flat! Some do though, and I think they are newer ones, which makes me think maybe they do distort with time. I don't know how old they are, but most of them were still in their plastic wrapping.

regards,
FF

Always prewet the filter paper with the solvent you are using, or , in the case of extractions...with the solvent with the greater volume ( i.e., the greatest amount). This prevents the filter paper from absorbing any of the solvent containing any of the reaction product, thereby causeing a lesser yield of the desired product.

The ideal way to fold SWIY's  filter paper is to include what is termed "flutes". These are creases in the filter that resemble an accordion. This is the "classical" way to fold your paper. The sharp edges of the creases increase the concentration of the solvent/solute at that point and generally speed up the filtering process. No, the whole surface area of the paper does't have to be in contact with the funnel walls. K.I.S.S.