I do not really wish to spell the difference or explain the meaning of bleached and unbleached. Wikipedia and a good dictionary does a better job. If still in doubt, go Google.
I look at it from another angle, that of a Barista who is concern whether it changes the flavor of the coffee altogether or if it does not really
matter at all. With a trained palate, ( although i still feel amateurish at times when tasting)I went on to brew a single origin washed Sidamo and cupped it with delish. I was disappointed, both coffee taste similar. Well, the coffee is good but I was expecting a paper taste in the unbleached filter but.....there isn't anything to shout about!
It strikes me to get all my 5 senses in action;
1)Visualizing the dimension and discovering that the unbleached is shorter in length- 9.7cm as compared to the bleached- 10.3cm but both having equal length.
2) Putting it close to my ear drums and flicking the edge of paper to try determine the thickness of it but to no avail. They sounded the same. If to gauge whether the thickness plays any difference on the weight or not, since my sense of hearing is not really superhuman ability, the weight test in a scale prove no difference separates the two. Next!
3) I began to smell both the filters. As I was expecting the smell of paper to come from the unbleached filter, again I assumed wrongly. The unbleached smell neutral while the bleached filter ironically smell like paper. Or could it be that all our writing paper are bleached and hence that particular scent is considered paper to us? Then what does paper smells like then?
4) I then began to run my finger across the grain of the filter. At time rough and then smooth. It felt the same too. This experiment is just about to get interesting.
5) Last but not least,the sense of taste. I have did that initially by brewing the same coffee in both filters but nothing really separates the two so I made up my mind to preheat the filters in the V60 and take notes of colour transfer in the cup and also the flavor of the charged water.
If the images above is even helping to shed some light, you can see a difference in colour discharge in the water on the first pour. The second and third pour shows no other difference in colour BUT A BIG DIFFERENT in taste. Next, to the cupping table to cup the water from the 1st, 2nd & 3rd pour of both filter papers.
Water in Unbleached paper test comparison:-
1st pour- Feels exactly like Licking a page off a newspaper. Try it if you have yet experience licking paper. :)
2nd pour- Slightly better then the 1st pour and taste like any normal hot water but with a tinge of taste you get when drinking water off a paper cup in a bank. Very light paper cup flavor. Almost non-detectable to an untrained palette!
3rd pour- Perfect and very normal!
Water in Bleached paper test comparison:-
1st pour- same flavor I got while cupping the water from the 'unbleached 2nd pour'
2nd pour- same flavor I got while cupping the water from the final pour in the unbleached experiment. Good to go!
3rd pour- Not necessary and I didn't even bother tasting. Perhaps I should, maybe the water might have taste too light and clean after all the filtering.
My humble conclusion:-
It's still alright to use the unbleached version in cafes, as the experiment have proven that the water taste normal after the 2nd and 3rd flush. A barista will need to flush the filter and cup anyway, in preheating to prepare for a pour over brew. If there is any negativity to it, it is the thought of having an additional step of an application to flush thrice instead of just once or twice.
Of course there is no motivation in doing so, unless the costing of the unbleached paper is so much that it makes more economical sense to start ordering the unbleached and forgetting the belched ones.
A thought to ponder though, while I leave you to start your own experiment, could it be like the natural and wet coffee processes that is being practiced in farms, same coffees can taste so different in two different processes so much do that the good people in Hario wishes to highlight a different tasting coffee via the creation of the bleached and unbleached. On a hindsight, as many preferred using the bleached with the argument sake of paper flavor that the unbleached gives, have you ever think what happen to all the chlorine that was use to bleach this papers and where all this chlorinated water is disposed? Perhaps is more green and Eco friendly to use unbleached filters after all for the sake of no chlorine being used in the production.