Step 4: FLAME polish

Here is the tricky part where some skill is involved. The basic goal here is to essentially use the fire of the torch to melt the plastic, without burning the plastic. Burning plastic is characterized by bubbling and black specs. If you burn your plastic, sand off the damaged material and try again.

Place your plastic onto a non-flammable surface. I used a cleaned welding table. Pull the plastic out so the edge of it is hanging. This will keep it from melting a little bit and picking up the texture of the surface it is resting on. Turn on your torch. Since you are using a propane torch that produces a carbon monoxide gas, make sure you are using this tool in a well ventilated area.

You generally want to flame on your torch to be strong. You want to use the crisp,blue, inner flame to actually polish the plastic, but you should always be aware of the rest of the flame because of its ability to interact with your plastic. Now, with the lit torch, very quickly move over the areas you want to polish. This motion is almost like quickly brushing hair. You want to move fast so you do not burn the plastic. The plastic will retain heat energy, meaning that the more passes over the plastic you do with a torch, the more potential there is to burn the plastic. in addition, because of this energy being put into the plastic, there can be a tendancy of warpage, just clamp down the plastic (away from the areas you are polishing)

You will know when you have done the right thing with your plastic when it reaches its polished finish. I almost looks like a bead of water is running across your material when is it reaching the appropriate melting point. In the final image, i have a picture with what a polished area looks like (on the left) and an unpolished area (on the right). As always, it is best to test your skills first. Grab a piece of scrap where you can refine your skills.

You now have a piece of plastic with a finished edge.
<p>Thanks, will try this on my 3D-printed PETG parts :)</p>
<p>There is a youtube video that says that a propane torch doesn't get hot enough and you need a MAPP gas torch. Maybe that's why his results were less than optimal.</p>
Although I haven't seen optimal results from torch polishing, I'd have to agree with pfred2. The best results come from the best tool for the job in skilled hands - your end results (as seen in the pics) do show scratches. You'll (likely) never get better results than using buffing wheels &amp; compound - plus, far fewer ruined material. Yes, fire can be fun, but in this case there's a better way. <br />Having said that, if a torch is all you have... fire it up!
Meh, my piece I was polishing was some scrap that was only sanded to a 120grit. Had this been a piece of plastic I cared about I would have sanded it to at least 320grit and then flame polished. That makes it look plenty slick
I am confused as to why you didn't show or detail this in your instructable, may people just look at pictures would see your end result and think that's not giving a great finish. You may not care about the plastic but you could care about the instructable.
Torch polishing works but actually polishing achieves optical accuracy. Which is to say it just comes out better. So put down the torch and just grab some polishing compound and do it. It is a bit more work, but the results are worth it.
I disagree, the best result come from what tool the user is best skilled with. Plus, fire is way more fun!
Your opinion varies from professionally qualified ones. I think I'll side with the pros. In fact I know I am. Flame finishing plastic is a neat trick, but mechanically inferior to polishing. Whether you agree or not is irrelevant.
I feel like you are not grasping the point of this instructable, which is not about what type of polishing technique is better, but is only about how to flame polish plastic <br> <br>Continuing in the direction of this conversation, I am not sure why you would have to side with a pro on about how to have more fun, but as someone who has worked and continues to work professionally with plastics, I can tell you that fire is indeed the more fun process :) <br> <br>In addition, the best result will always come from the tool a person is best with.
Excuse me, I thought this article had something to do with polishing plastic. Now you've made it out to be all about fun, and misinformation. <br> <br>Expert testimony is accepted admission for dispute resolution. Now you know why I used professional opinion stating my case. <br> <br>The best result will always come from using the best process. Tools are a part of a process but methods matter more.
How about stringing a few together and forming a coherent sentence?
could you also use a heat gun for this??

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