I tend to work with foam a lot. Same goes for closed cell PVC boards too, plastic stuff. Mainly because I've grown too damn lazy to make things out of wood anymore.
Last month, I got one of these babies:
|Hot knife, I am.|
But alas, it wasn't as perfect as I thought it was going to be. Over the last couple of days of playing with this monster, I've learned a few things, so I'm going to share it with the interwebs so you guys don't make some of the same idiot mistakes I did.
1. It's bloody sharp and hot at the same time
Ever heard of the phrase 'like a hot knife through butter' ? a hot knife pretty much sums up that experience. The first time you stick that knife through some foam feels pretty amazing, but you tend to forget that the blade tends to be of the 'extremely sharp, will make your fingers into bacon' variety and since the material you are working on is melting, it's pretty damn easy to slip if you put too much force in it.
So far I've been lucky that the only two times it slipped the knife only hit the table, but who knows when that luck is going to run out.
|Or you could pretend it's a lightsaber.|
This goes out to people using a hot-anything. Hot glue gun, heat gun etc, I don't care if you're doing it on the table or on the floor, cover your legs with something. Wear a thick pair of pants, cover them with a towel, newspaper, ANYTHING.
I've learned first hand that melty things tend to drip, and those drips also happen to be damn hot, the last thing you want before a con is to have a mighty blister on the inside of leg because a rogue bit of plastic decided to say hello to your pale fleshy thighs.
Also if you can help it, wear gloves. Manual dexterity will be compromised but its better than having damaged digits.
3. Do it in a ventilated area
In case you forgot, foam and plastic are made of chemicals. Chemicals that are pretty damn bad for you if you inhale them in fume form. In other words, it stinks. A lot.
Wear a face mask and do it somewhere that has lots of ventilation, like next to a window or something. Get a fan, blow that stank outside. You'll thank me when you're not inhaling little particles of plastic.
I can't stress this one enough. What part of working with a hot ass, sharp knife should you be doing in the dark? none of it. You're likely to cut or burn yourself if you can't pay full attention to what you're doing. I've cut myself plenty by using a boxcutter while not paying attention to what I'm doing, and having shitty lighting doesn't help either. Work under a lamp or something if you have to get your stuff done at night. Which you likely will, the night before the con.
Which brings us to our next point...
5. You will destroy your shit if you're not looking
I don't know about other models of hot knives, but this one is basically a modified soldering iron that has a knife on the tip instead of a rod. The blade portion is removable for replacement purposes but the barrel of the knife is also hot when it's in use.
This has lead to a lot of scarring and burn marks on the Sintra I happened to be cutting (because I wasn't paying attention to what the rod was touching) and it has outright melted some of the foam I was working on. Watch where you're poking that thing and you'll be fine.
6. Wipe often.
Plastic gunk can and will accumulate on your blade. With avengeance. It might burn, it might just bubble or it might just sit there and muck up everything it touches.
Get a rag or a wad of newspaper you're willing to destroy to wipe that stuff off with. If you're too scared to touch the knife (as you should be) you can just rub the knife against the cloth instead to get stuff off, but it will be harder to do once it's cooled so it's the first thing you want to do once you turn the power off.
Oh, your knife will also start to turn black the moment you start using it. This is because of oxidization or flammable stuff getting in contact with your blade. There's nothing you can do about it besides embrace the soot.
Chances are it will look like this after a few uses: