I use single infusion mashing with a modified picnic cooler. When attempting to mash out I use a good deal of near-boiling water just to raise the temperature from the mash to 170 ºF (77 ºC). Not having the ability to apply direct heat to the mash tun, I was wondering if I could, like in decoction mashing, remove the thick portion of the mash, boil it and return it to raise the temperature to mash out, thus not having to add additional water. Would this extract tannins and “grainy” flavors since the beer was made via the infusion method? If this is feasible how much would I pull off of the main mash to boil in order to achieve the mash out temperature?