Part 3 of this series describes various filter paper cone folding techniques. Read on to see the options for getting a good seal over your conical funnel.
|Quadrant folded||Fold the paper into exact quadrants.
|Standard, very common technique|
|Quadrant folded||Fold the paper into quadrants, then open to form a semicircle, identifying the center line.
Next, make two further folds, either in the same or opposite direction.
The result is a 60° cone when the paper is opened out.
|Allows the paper to filter in a more balanced manner than standard quadrant technique
Has certain disadvantages, especially if the precipitate tends to creep
|Quadrant folded||Fold the paper into quadrants.
Make an extra fold at a slight angle from the center.
The result is an angle at the apex of the cone slightly more than 60°.
|Can provide a better fit when wet and loaded with precipitate|
|Quadrant folded||Fold the paper into quadrants,
Tear off the corner of the outer fold
|Enables the rim of the filter paper cone to seal better against the glass funnel than a standard quadrant fold
Tearing the corner is better than cutting as it tends to stagger the two thicknesses of paper.
Fold the paper into exact quadrants.
Make a further two folds bringing the outer edges in two the center line.
Open the folded circle and invert.
Push alternate folds into the center, making a neatly pleated arrangement.
|Pleating filter papers is a very widely performed technique and offers improved flow characteristics compared to c|