To use, put over the filter end of a bombilla, and pull the string tight. Use the bombilla as usual with a high ‘polvo’ content. The paper will filter out the thinnest of powder.
Some Yerbas have a very high ‘polvo’ content. This is sometimes described as ‘dust’ and consists of extremely ground yerba leaves, not actual dust! The advantage of a high ‘polvo’ content is that the yerba is much more intense in flavour, but it can be tricky to avoid the bombilla from clogging. The best method is to allow the yerba to absorb water for a few minutes before using, but you may opt to use a paper filter if you find the bombilla still clogs. The yerbas that this is applicable to is usually the very traditional Brazilian Yerbas used for ‘Chimarrao’ – yerba mate prepared the Brazilian way.