# Mold for HDPE



## Albinogek

I am planning on making a mold out of plywood to cast some HDPE & am wondering if anyone knows or has tried placing aluminum foil in it so that the HDPE does not go into the sides of the mold, causing it to stick. I am planning in putting the mold in the oven, with the pieces of HDPE in it. I've seen people use wax paper, but am not sure if it would withstand the heat. Any advice would be greatly appreciated.

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## bigron

most people melt the hdpe in a metal pan like a cake pan 8x8 or a 9x13 then cut the shape they want you will probably find better success like that


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## Albinogek

I appreciate it Bigron, but do they place anything else? Meaning do the place any clamps with a board to take all the air bubbles out as well as make it all uniform (same thickness all the way across)


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## JTslinger

CanOpener has a video series on YouTube on how he works HDPE start to finish.


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## Phoul Mouth

Albinogek said:


> I am planning on making a mold out of plywood to cast some HDPE & am wondering if anyone knows or has tried placing aluminum foil in it so that the HDPE does not go into the sides of the mold, causing it to stick. I am planning in putting the mold in the oven, with the pieces of HDPE in it. I've seen people use wax paper, but am not sure if it would withstand the heat. Any advice would be greatly appreciated.
> 
> Sent from my iPhone using Tapatalk


Do not put the mold itself in the oven. Put it in an aluminum pan lined with wax paper. Yes, wax paper will stand up to the heat, that is what it is designed for. Bakers use wax paper all the time for baking cookies and such because they just slide right off and leave no mess.

Make your mold to be approximately the size of the aluminum pan you will use. Sure, you can line the mold with aluminum foil, but wax paper would probably be better still. Once the plastic is melted and fusing take it out of the pan, flip it into your mold and clamp it down. The purpose of the mold is to stop the HDPE from bending and twisting while it is cooling.

If you put the mold itself in the oven you risk a fire, any plywood you used de-laminating, and toxic fumes from the various glues and waterproofing chemicals. DO NOT DO THAT. I repeat, DO NOT DO THAT!!!!!


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## Albinogek

Wow, thanks for the insight Phoul Mouth. JT do you have the link for the YouTube video?

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## Devil'sRival

Do NOT use wax paper on hdpe unless you want this. 


You can use baking paper instead.


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## Albinogek

Thanks Devil's Rival for the info. What size of pan did you use?


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## Teach

Albinogek said:


> I am planning on making a mold out of plywood to cast some HDPE & am wondering if anyone knows or has tried placing aluminum foil in it so that the HDPE does not go into the sides of the mold, causing it to stick. I am planning in putting the mold in the oven, with the pieces of HDPE in it. I've seen people use wax paper, but am not sure if it would withstand the heat. Any advice would be greatly appreciated.
> 
> Sent from my iPhone using Tapatalk


I've done this and I don't recommend it. The aluminum foil stuck to the HDPE in a way that made it impossible to peel off the HDPE. It won't be terribly difficult to deal with as it is only on the bottom and 1 inch sides of the HDPE board that I made so when I cut out my frame only the surface of one side of the frame will have the aluminum foil stuck to it which should just file off. I'm hoping it doesn't clog my file teeth.

It's not a deal breaker but still save yourself a headache. I only tried it because the 8x8 teflon coated cake pan that I had was missing half the teflon coating......it was old so I thought I'd just line the pan with tin foil to prevent it from sticking to the pan.......well that part worked very well. It did not stick to the pan. But it did stick to the HDPE and won't come off easily.

Also, don't use your house hold oven. It will stink up the oven and house and will cast bad flavours to future foods cooked in the oven and it's a nasty flavour that will make you want to throw the food out. If you can find an old convection toaster oven at a yard sale or similar source and use it solely for HDPE and not food.


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## Teach

Albinogek said:


> Wow, thanks for the insight Phoul Mouth. JT do you have the link for the YouTube video?
> 
> Sent from my iPhone using Tapatalk


This is one of the best out there made by Canopener.


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## Albinogek

Thanks Teach! Will now have to get me a toaster oven. Thanks for the info, it really helped shed some light on the process.

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## Phoul Mouth

Teach said:


> Wow, thanks for the insight Phoul Mouth. JT do you have the link for the YouTube video?
> 
> Sent from my iPhone using Tapatalk
> 
> This is one of the best out there made by Canopener.


I just got a new convection toaster oven as a gift and was waiting for trash day to toss my old one. Now I shall most certainly be keeping it. This is probably the easiest method of making HDPe sheets I have seen. I even have some old crappy brownie pans to used for it as well. No need for a separate mold? Hell yeah.


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## Albinogek

Way to go! Not too crazy about having to buy one, butt Momma won't be too happy if I use our oven! Lol

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## Toolshed

AG, what you'll be looking for if anything at all is PARCHMENT PAPER. I'tll be in the baking aisle as well. It is nonstick and doesn't have anything impregnated in it to leech out or allow the stuff to grab onto. I've not tried it with plastics YET....

MUAHAHAHAHA!!!!

I've raided a few of the local goodwill stores and not a single toaster oven to be had....I'd hate to have to go buy a $30 one at BigBoxBilly just to destroy it with HDPE....


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## Albinogek

I know that's right! Don't know if Craigslist would be any better. Have to be careful with all the weird people out there.

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## Chuck Daehler

I saw a vid made by a young man who is also a newish member of this forum, lives in UK. He tried a plywood mold in the oven and could not get the HDPE blank out without destroying the mold...no release paper.

Wax paper and silicone treated baker's paper are two different things. The wax melts giving you a coat of it on the HDPE billet as shown above by a poster.

Your best bet and used by all HDPE SS makers by the way who melt HDPE, is to melt it in a square or rectangular cake mold as shown in the vid ABOVE. Band saw the blank from the billet. Save the pieces to remelt to make more billets and blanks. You will have about 50% pieces and the rest sawed out blanks...so saving the cuts is worth while.


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## Albinogek

thanks for the info Chuck, I think we saw the same video... Art of weapons. I am leaning more towards using the 8x8 brownie pan as was previously mentioned. I am in the process of getting some HDPE buckets, milk jugs, detergent jugs & of course a toaster oven. Takes time to get everything, plus money!


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## Teach

Honestly, for the tiny price of a small 8x8 cake pan that is teflon coated like Canopener and I use it's not worth messin around with parchment paper or any other non stick layer which the teflon coated pan already has. When you think about it......for the cost of the parchment paper you could probably come close to being able to buy another teflon coated cake pan.

Once you use a toaster oven for melting HDPE, I'd have it to use for nothing else from that point on. The process is not hard on the oven itself - that's what it was designed to do right! But if you try to use it for food thereafter it will impart terrible tastes to the food from that point on. I've not tried to wash it out to see if it changes that aspect or not, it just became my dedicated HDPE melting oven from that point on.

Most HDPE sling shots range between $20 and $30 each. If you get your hands on a used toaster oven for $30 as mentioned essentially it's paid for itself with the first HDPE billet/board you make with it as you should get a minimum of two sling shots from it.........two full size with maybe a small BB shooter from one of the cut off pieces if you lay it out on the billet well enough.


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## Albinogek

That's what I am planning on doing, buying a toaster oven for the sole purpose of melting HDPE. I have not had a chance to go & price the 8x8 pans at Wally World, so if they are Teflon coated there is no need for baking paper. The HDPE doesn't stick to the pan?


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## Teach

Albinogek said:


> That's what I am planning on doing, buying a toaster oven for the sole purpose of melting HDPE. I have not had a chance to go & price the 8x8 pans at Wally World, so if they are Teflon coated there is no need for baking paper. The HDPE doesn't stick to the pan?


If you watch the video, it shows the HDPE billet just dropping out of the pan. So no, it shouldn't stick.

I've used old pans with the teflon coating missing in places..........save yourself some grief and don't use anything but a new pan. I literally had to destroy the pan to get the HDPE out. No there is a case for using parchment paper, it would have prevented that from happening. If you can.......use a new pan with no teflon coating missing.


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## Albinogek

Will do!


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## Urban Fisher

I'm no expert, but I have made quite a few slingshots with the stuff. As already stated, the easiest way is a cake pan. I bought a cheap non-stick one from a dollar store.

I did however start out with a wooden mold I made. I lined it with parchment paper, filled it with HDPE chunks and threw it in my oven. It worked well for awhile, but the wood did start getting charred a bit from being baked a lot. That is when I decided to just buy the cake pan.

Once I bought my cake pan, I cut out a piece of plywwod (1/2" I think) that fits into it like a lid. I throw my HDPE chunks in the pan, melt it, pull it out of oven, use a small board to press it firmly (releasing air bubbles), add more HDPE chunks and repeat until your mold is full of melted HDPE (it tends to shrink some when you melt it). Then when it's fully melted in the pan I remove it from the oven, put parchment paper over the top, add my wooden lid and clamp it down. Let it sit for a few hours until it cools then remove from the pan. You basically should end up with a big solid chunk of HPDE that works like any piece of wood.

Now this is the way I do it! There are many other methods and none of them are really right or wrong....just some easier than others. The stuff is great slingshot material for sure!!! Many colors to choose from, the stuff is free, easy to work with, indestructible and it floats! The main advice I can give is just start playing with it. It has properties that are hard to explain, but the more you work with it, I'm sure you will figure out your own methods. If you ruin the first mold or two...no biggie, again it's free and worst case....just re-melt it!


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## Albinogek

Really appreciate the insight Urban Fisher. Your way makes it sound easy

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## Chuck Daehler

I also tried al foil..same results as Teach's...stuck to the HDPE. I used Armorall spray and that was a pretty good release agent, it's silicone and nothing sticks to it. I made my HDPE billets THICK so surface blemishes wouldn't count and I sculpt my super ergos anyway so no surface of the original billet is anywhere close to the finished surface. Since I can't get baker's paper here I had to use al foil sprayed with protectant. Most of it peeled off so fortunately with my method of sculpting any left just rasped off.


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## Themexicanshooter

One good mold you can use is glass mold. it makes a very smooth finish.


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## Themexicanshooter

I would not recommend using plywood. I've used baking paper in the past and it's worked great, just don't over heat


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## Chuck Daehler

I've made six HDPEs out of three billets...2 SSs per billet. I used an old baking pan with aluminum foil as a liner since all surfaces must be rasped or thickness planed anyway. I sprayed the aluminum foil with automotive silicone spray used for a protectant for vinyl and such...it released the al foil very well.


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