Your new favorite cosplay tool: the hot knife
Let’s take a few minutes to talk about our new favorite tool for finishing fabric edges…. the hot knife! For those who are unfamiliar with this product, a hot knife is similar in size to a soldering iron with changeable tips. Once plugged in, the tips will heat up so that you can use the hot end to cut or heat various materials. Hot knives are pretty cheap too - the below set will run you $22 on Amazon.com.
Many cosplayers already use hot knives to cut foam and other prop materials, but you can use a hot knife on fabric too! So long as your fabric is made from unnatural material such as polyester, a hot knife will melt and slag the raw end of your fabric, turning it into a hard, plastic-like line. However natural fabrics like cotton will not melt and slag - instead these will simply burn away if you try to light them on fire or use a hot knife. To test your fiber and perform a burn test, follow these steps.
But why would I ever want to melt my fabric??
There’s a few reasons!
Edge finishing. Is your fabric edge an odd shape, or something that can’t easily be rolled or serged? Slagging or cutting with the hot knife prevents your fabric from fraying, and allows you to create whatever shape your design calls for.
Distressing. We used the heck out of the hot knife for our Sakizou costumes, since it required so many raw and distressed edges. Holes and rips can look a little strange if your fabric is the kind that frays easily - what looks great now may not look so hot in a day or two when threads are beginning to unravel. Sealing the edges of your fabric with a hot knife guarantees that the edge will not fray, no matter how much you wear your costume. We used the following methods while creating our Sakizou cosplays:
- Slagging while cutting - on satin, I first traced out my distressed pattern while using chalk. I then chose one of the tips that came to a point, and “cut” along that pattern with the hot knife. The heat from the knife burned through the satin and sealed the edge in one go. A heavy piece of cardboard should be placed under your work so that you do not accidentally cut or burn your table. This method is great for weightier fabrics or ones that will not roll under the knife.
- Slagging after cutting - on chiffon, the above steps were difficult to do since the fabric was so prone to sliding. Instead I first cut the basic shape I wanted with scissors. I then used a flat tip and ran the hot knife along all edges of the fabric to seal. Be careful of the heat setting and how long you stay in one place while using this method, as light fabric can melt easily.
Some general hot knife tips:
- Don’t over-heat your knife. Test first to determine which temperature is best for your fabric; something too hot can melt away your fabric more than you intended.
- Don’t leave your hot knife unattended or around animals/children. It’s really hot!
- As always, make sure you use your hot knife in a well-ventilated area since you are in essence melting plastic, and different polyesters can give off fumes.