Ah, the Smelter, the gateway into start smelting iron to upgrade your blueprinted tools, such a great thing, but it does come in small, and when the game was first released and the Night of the Living Smiths update was here, it was all gems, but now the new update has come, it's one third coins now, and the rest is gems, which is a great helper.
Level 1: Campfire Cookpot
The initial smelter buy which has no level is glitched, and is also named the Campfire Cookpot, but this is the real level 1 smelter, the only way to describe it's looks as a spit-roast turnstile, but with a cookpot hanging from it full of lava, with a fire blazing underneath. This costs 350 coins to upgrade.
Level 2: Rusty Barrel
After the Campfire, you got the metallic barrel, with rust patches. There is lava on the inside of the barrel. This costs 600 coins to upgrade.
Level 3: Bronze Smelter
This is a slight upgrade in looking-wise, it looks like the Rusty Barrel, but wider, made of Bronze, and the lava inside is barely visible, but it's there. This costs 850 coins to upgrade.
Level 4: 1980s Microwave Oven
This is one of the more interesting smelters on the spectrum from 1-12, this is just a microwave oven, it has a handle to open the door, the inside isn't seeable, it has 2 red buttons, the rest are black, and it just looks like a microwave oven. This costs 1100 coins to upgrade.
Level 5: Science Fair Volcano
Now, this is definitely one of the funnier ones, looks like you became a thief and stole from a science fair, poor kid who lost this, it's a papier mache volcano, with fake lava leaking out the top, there is a 3 panelled background that says Volcano in blurry writing, and there is a blue ribbon, that is assumed to be a #1 winner ribbon, this is where it starts costing gems, and this specific one costs 55 gems to upgrade.
Level 6: Cast Iron Smelter
This is a more dull smelter, it resembles the Rusty Barrel in appearance, but it's not bronze, it's made of iron. This costs 65 gems to upgrade.
Level 7: Smelting Furnace
We couldn't escape the iconic furnace from Minecraft, and neither could people like Tiny Titan Studios couldn't either, so they added the minecraft furnace into the game, this costs 75 gems to upgrade to the next one.
Level 8: Fusion Smelter
This smelter has a more sci-fi theme, it looks bizarre enough for me not to describe it, but I do insist you look at the picture, that looks better than what I could try to describe. This costs 85 gems to upgrade to the next level.
Level 9: Dark Iron Smelter
This one is easier to describe, all I can think about while looking at this smelter is that I can see a face, with a crown, spewing lava, it haunts me. There is a horseshoe shape as the mouth, two beady eyes and a crown full with lava. This costs 95 gems to upgrade to the next one.
Level 10: Hydrothermal Inductor
This is where the terms for naming the smelters becomes more technological, I can describe another face, resembling the new Pyrocynical avatar, the TV head, with 3 holes coming out it of, and a suction pipe out the side, it's all red, so it's assumed to be full of lava. This costs 105 gems to upgrade to the next one.
Level 11: Dark Matter Inductor
More scientific now, it harnesses a dark matter sphere in a glass orb to smelt, it kinda reminds me personally of the Eye of Sauron, how it's unblinking, there is a pool of lava just under the Dark Matter, on the bottom of the orb. This costs 115 gems to upgrade to the next one
Level 12: Laser Smelter
This is the last level, the max, so it has no gem pricing, but the pattern would tell me if there was any more levels in future updates, it would cost 125 gems. It looks like a bowl mixer with whisk, but there is a bowl full of lava, and the mixer is excreting a laser.