[quote=“Chinaski1217”][quote=“rebuiltcellars”]The big downside of a metal kettle for a mash tun is heat loss; you will drop in temperature A LOT unless you insulate reasonably well or have some method of adding heat back almost continuously during the mash. I used to try direct heating, and discovered that you need to continuously stir to avoid creating big thermal gradients in the kettle. Best to avoid that problem by keeping the tun insulated.
I’m curious, do you plan to fly sparge or batch sparge? What is it about the plastic cooler that makes you nervous? I went the other way a few years ago, and have never considered going back, but everyone’s process is different.[/quote]
I batch sparge. And the more I read or hear, it seems like your experience is common in regards to maintaining temperature in a thin-walled kettle. I don’t own a pump to recirculate and don’t really want to buy one. And a number of the kettles I see aren’t meant to be heated directly.
I guess what concerns me (and I realize this may spark an unwanted debate) is that I’m not exactly sure how safe it is to maintain mashing temps in a plastic cooler that may not be meant to handle those temps. Or maybe it’s fine, and I’ll just keep doing what I’m doing. I’ve read threads on this and there seems to be no consensus.[/quote]
Aaaaand, then I found this (thread here:
I asked my homebrewing plastics chemist friend for comments, so we could get some real facts and not just specualte. He read this thread and sent me the following email…
"I forget whether the Rubbermaid and Igloo coolers are polypropylene or polyethylene but both are very similar plastics that vary mostly in there temperature ranges. Both are relatively low temp plastics and very safe for food contact. The only worry about using hot liquids in either cooler is that the plastic will soften at temps approaching 200°F.
I used to use a Gott cooler for a mash tun and used a false bottom with screws for feet to hold it up above the spigot. On one occasion, I did a decoction and after adding the boiling grist back to the cooler, there was enough wort at high enough temperature that when I turn on my circulating pump, the vacuum pressure on the FB caused the bolts to pull down through the bottom of the inner wall. I never had a problem with regular infusion mashing though. Eventually, the inner wall will buckle a bit from multiple hot water infusion.
I enjoyed reading some of the comments on the NB forum. You can post this there if you like. It’s amazing the tack that a discussion can take when everyone works off of speculation and not information. PP & PE are only related to PVC because they are both polymers. From there, they are quite different. Many PVC’s have plasticizers added to soften them up. It’s the plasticizers that are liable to leach out and cause health problems. Unless you work in a PVC factory, the PVC itself is not worth worrying about. It’s the Chlorine in PVC that makes it so potentially dangerous but primarily at processing temps, not use temps.
Cost has nothing to do with whether a polymer is safe or not. Most polymers are food grade. Many don’t have the certifications that are necessary to sell them as food grade. PP & PE see so much food contact use that 99% of them are designed for food contact. Do you think that they’d let you put water in a non-food grade container (I know you don’t Denny)? The polymers price is based on the cost to manufacture it. PP & PE are cheap because their chemistry is so simple. Think of them as a close cousin to candle wax. From there, most plastics are priced by their temp capabilities. I’ve worked with some that are over $50 a pound. They get lots of use are medical instruments and aircraft interiors.
The polyphenylene sulfide (PPS) that is common on March pump heads is the binder that sticks the teflon to your cookware (you didn’t think they could get teflon to stick, did you?). The polysulphone of the quick connects is also used to make the interior panels of aircraft because of their low flammability and low smoke emissions. BTW, the vinyl hose we all use around our home breweries is PVC! I’m sure it has plenty of plasticizers in it to make it flexible."
Denny Conn, y’all. Seems pretty OK.