one way valve tells you to wash filter paper with hot water before brewing coffee. Although we have already compared the differences between non-bleached filter paper and bleached filter paper, and this is not the unique difference, the quality of filter paper will also affect the flavor of brewing coffee and the good water flow. Though its minute differences, and we can feel that from the coffee of cup.
The most important part, you must choose the suitable size of filter paper to match the brewing method, and pay attention to the thickness of filter paper. If the filter paper is too thin, the water will penetrate too fast, while thicker filter paper will retain more coffee fat during brewing. If you are looking for thick filter paper, you need to afford a higher price, but fortunately the price difference just a little.
Against the choice of bleached filter paper or non-bleached filter paper, the most important thing you should consider the coffee flavors or the impact of an environment?
If you want to contribute to the environment, you can buy non-bleach filter paper and wash it before using. On the other hand, if you are worried about the coffee with paper taste, you can wash the filter paper twice, or use bleach filter paper (recommend to use oxygen bleached filter paper).
And also, the quality of filter paper is also important, the cheap bleached filter paper obviously has a paper taste in the coffee, and if you are care about the paper taste, you can use the better quality non-bleached filter paper.