Tuesday, February 24, 2015

Six things I learned while working with a hot knife

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.
Set me back about RM 60 from Multifilla which I felt was a great investment; clean cuts! There are other models available which are probably better but this was the only one I've seen for sale so far that didn't look like it was made to cauterize dinosaur bites.

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.
2. Protection, please.

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.

4. Lighting!

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:

At the end of the day safety is still tantamount to you getting your props done on time so I hope the article was useful, and stay safe!

Saturday, February 21, 2015

[Tutorial] Quick n' dirty steampunk goggles

This whole thing is 90% foam. Believe it!
Need a pair of steampunk goggles on the fly? making these would set you back a couple of hours at most, and can be made of random junk lying around your house.

The goggles I made were meant to be pinned to a top hat I made (no tutorial sorry, not unless I decide to make another hat!) so they CAN be used on your face but they're nowhere near as comfortable and can be kinda flimsy for actual wear. But they definitely work if you just want a pair for show.

NOTE: This tutorial does not include any measurements whatsoever, because your base materials might vary.


A reasonably sized cardboard tube (any tube shaped material would work actually)
Foam (two thicknesses, preferably between 2mm - 5mm)
Scrap cloth or faux leather
Scrap transparent plastic sheet, mine came from a plastic file
PVA glue (or favourite foam sealant)


Scissors/ boxcutter knife
Contact Glue
Rub N' Buff in Antique Gold
Acrylic Paint
Needle and thread


3D paint
Tiny screws or thumbtacks

The first order of business is to find a reference for what you want to make your steampunk goggles looking like. I wanted something more vintage looking (without all the extra fancy stuff) plus I need to do it really fast (because, I tend to do shit last minute) so I picked a very basic design.

Cut the tubes and fit the first foam layer

These will form the main 'body' of your goggles. Take your tube and cut it in half and then cut the other end slightly slanting so they will fit around your eyes comfortably. If you aren't going to wear them you don't have to cut them to an exact fit.

Next cut out two larger strips of the thinner foam and wrap it around both tubes, glue them down and trim off the access. Once they dry, coat the outside of the foam with a sealant and let it dry.

While waiting for them to dry, measure out and cut adequate amounts of scrap cloth, elastic or leather to make into your 'strap'. Make a short one to act as the nose bridge of the goggles and a longer one that will go around your neck/head/hat/whathaveyou.

Make the lenses
Use the 'front end' to measure

For the 'lenses' cut out circles from your transparent plastic sheet and then glue them onto your tube. Don't worry if they're too big, you can trim them off later. You can use tougher plastic or even coloured material for this step, as long as it's semi transparent anything works really.
They will more or less look like this
Optionally, you can also paint the inside of your tubes if you don't want people to see that they're actually made of cardboard rolls :P I painted mine black but at a later stage than I should have. Lesson learnt!


Once you have trimmed them, cut out a pair of 'rims' for your goggles. I wasn't super careful when cutting mine out so they're a little uneven but I did trim them down somewhat. Once they're ready place the outer rim on top of the goggles and glue it down. 

This will act as sort of a 'sandwich' to hold the lenses in place and make it look cooler/hide all your ugly glue. You can also glue an additional ring of foam on the back of the goggles to simulate padding or to just make it more comfortable if you do intend to wear it later.

Here is where I added little drops of 3D paint to the outer rims to simulate rivets, you can also use 3D paint to make them look all regal by painting decorative patterns on them if your character is of the fancier persuasion.

Coat the outer rims with sealant as well. You can add little screws or thumbtacks as well but do it after you've sealed everything.

Paint paint.

Paint up your goggles to be with a base coat. Black is preferable. You may need 1-3 coats depending on how thick your paint is, just be careful to avoid dripping any on your lenses. Allow to dry thoroughly in between each layer.

Now here's the fun part.
After the base coat has dried, break out your Rub N' Buff and use your finger or a brush to start painting the entire body of the goggles, buff them out when done.

If you don't have/want to use Rub N' Buff, regular copper coloured acrylic paint will work just as well.

Take a bit of care to avoid painting on your lenses as usual.


Once everything is done, take your straps and either glue or staple them to your goggles. Optionally you can cover the staples with a bit of paint or foam, though bear in mind that glue is not as good as tacking the straps down and should be treated as a temporary measure.

After that you're pretty much done! I might write a more proper tutorial later because I am going to be making more goggles, hopefully with more comprehensive instructions.

Happy building!