Melting copper for practice

So I'm starting to get into gold refining after a couple months of research on everything and today I was practicing my melting. I purchased some tiny copper shot pieces to try melting. I glazed my crucible with some borax and then poured about 15 grams of copper into my dish. I have the TS8000 and I used my Map Gas and when that finally melted (about 15 minutes later) I tried pouring it and it wasn't the greatest pour, shocking lol. But after dumping it in water to cool it off, i tried melting it again but halfway through my Map Gas ran out so I had to use my propane tank. I tried melting that thing for probably 45 minutes and it slightly melted but never came close to being able to actually pour the thing. When I gave up the copper blob was stuck to the silica melt dish and in frustration I just dropped the whole thing into my water bath, probably not the greatest idea, but the copper did come out.

So my question is: Is using propane vs Map Gas that much of a difference? Or was it because since it was a bar at the time of the 2nd melt, it would have just taken forever to melt it down. It looked like it was getting close a couple times but it seemed like my torch was spitting propane and messing with the flame. Also, is it normal for my torch to get cold and iced over after 15 minutes of running on full blast?

Sorry for the long post guys but any melting tips would be greatly appreciated!!

Mapp gas is a hotter fuel than propane, either should melt copper without the support of adding bottled oxygen (but without much heat to spare).

The torch may have enough heat to melt copper but the environment may suck that heat away as fast as you produce it, the type of melting dish itself absorbs heat and dissipates it, if it is sitting on a big heat sink it can absorb all of the heat away from the melt.

The torch uses gas as the fuel, the torch will not burn as well or as hot with liquid fuel, the fuel in the bottle is liquid and when used properly uses only the gas from the bottle, too high of fuel flow rates can pick up liquid, or if the bottle is not kept in an upright position will also deliver liquid instead of the more easily burned gas...

Liquid conversion to gas, when the liquid moves from the higher pressure of the tank to the lower pressure of the atmosphere when the liquid is converted to vapors (the principle air conditioning works on) the evaporation of the gas absorb heat around the bottle and the moisture from the air will freeze onto the bottle.

Too high fuel delivery rate can cause tanks to freeze, as the liquid is carried with the vapors the liquid being feed to the torch.
Bottle position can be important to the delivery of gas and not liquid fuel, with some systems a regulator may be needed to control fuel flow rate, maintaining the bottle in an upright position so vapors and not liquid are fed to the torch.

Larger or more tanks may be necessary for the liquid to convert to gas before being fed to the torch head.

Sitting bottles in a warm water bath during use can also help to keep tanks from freezing.