If you do get a variac, make sure you get one big enough to handle your equipment. It may cost a few bucks more but if you are running say 950 watts in your roaster, don't go with a variac that has a 1000 watt rating. Yes... technically it can take it, but running it at that close to 100 percent of its capacity is not the best method. Also as you boost the volts you will boost the watts you are using as well and can find yourself AT capacity or slightly over, again it can take a little overload but not the best way to do it.
Id get a 1200 watt or 1500 watt as a minimum...in this instance. Besides we all tend to end up upgrading eventually, let your machine grow into your variac and use the extra money youd have to spend on yet another bigger variac for your new rig ---pay for that new rig.
For the DC motor thing, I wont go there, there are actually many different ways to wind DC motors to make them behave differently as well. Series / shunt field/rotor etc etc. Don't feel bad that you don't have the savvy of knowing all this crap, those of us who do, didnt learn it overnight, we have worked with this stuff for years and years. Wasn't trying to insult you or anything, just point out that unfortunately, it's not just a simple thing .. that'd be too easy for us then
Heating elements yes, are technically just resistors, but once you start heating something to the point it is turning colors, it can start getting tempermental at that point about many things. Too much voltage.. not by much, they go pop .... too little... not by much and they are just 'warmers' instead of heaters... touch the thing somewhere and cause a 'cold spot' and it goes crack, followed by pop.... you get the idea..
Heat essentially is caused by current flow, voltage pushes that current, yet higher voltage means less current needed to make that heat.... all this flows through wires... heat is a bad thing with wires.... current flow through wires, in a sense is a bad thing too... the less we can get away with, the better, less voltage drop... due to heating etc etc..so yes 220 would be better on that mindview because it's using less current however in the usa where we live in a 115 world.. this can be problematic.
Our main problems are not necessarily the current the device needs, but dragging that current through the wires to get it from your fuse box TO the coffee cooker...the wires are the problem. so unless you were there when they built your house and demanded 12 gauge or even 10 gauge wiring to all your receptacles.. they probably used 14... because its cheaper, and code let them do it.
Ill shut up and go lay over by my dish now.
Aaron