Multi-rest mash by heating wort in a separate boiler?

[Brew_Meister_General]

Would it be a bad idea to mash at 40c, drain all the wort into the boiler, heat to 65-75c and then place it back in the mash tun? Would this have some repercussions like DMS?

 

[Yooper]

Would it be a bad idea to mash at 40c, drain all the wort into the boiler, heat to 65-75c and then place it back in the mash tun? Would this have some repercussions like DMS?

Yes, that would be a very bad idea. First, it would risk a too-high pH with the grain removed and cause some issues, and if it did get to 75C, it would/could denature the enzymes needed for conversion.

Either do a decoction by taking out the mash (mostly grain) and bringing that to a boil and add it back, or do an infusion of hotter water to get to the next rest temperature.