Plastic bags can be welded together with a soldering iron. The resulting seam is strong and water resistant. This is a very useful technique for making kites.

Step 1: Tools

You need some oven paper and a soldering iron.
I use a soldering iron with a flat tip and temperature control.

Step 2: Stack Materials

Place the first piece of plastic on some oven paper and mark the place where you want to make the seam. Then place the other piece over the first one aligning it with the mark.
The plastic sheets are slippery and they like to escape. You can make them stick in place by wetting them just a bit.
Now place another piece of oven paper on top of the plastic. You should be able to see the markings through the paper. This is why it is a good idea to use light colors and avoid black plastic.

Step 3: Welding the Seam

With very little pressure on the soldering iron move it along the seam to melt the plastic sheets. It is important that you hold the tip so that the whole surface of the tip makes contact with the paper.
The right speed depends on the thickness of the plastic. Low density plastic is easier to weld than high density because HD is thinner.

Step 4: Done!

When you have finished the seam, inspect it and test it by tearing it apart.
After some practising you will know the right speed and presure for different materials.

Use your new skill for making kites or inflatable stuff or something!
<p>I just tried the pencil gun &amp; 2 sticks method on thick black polythene - the kind you use to line building foundations. It worked great. The sticks I used had chamfered edges so formed a small &quot;V&quot; and I used a roller (the kind you use for gluing veneer or drywall taping) to press the edges together. I formed a sleeve that held water without leeks first time out!</p>
<p>I am always surprised by the different uses on how to use welding. I would like to find a welding project for myself. I hope that I am able to find the best thing for myself. There are a lot of things to choose from. </p><p>&lt;a href='http://www.suburbanweldingandsteel.com' &gt;http://www.suburbanweldingandsteel.com/&lt;/a&gt;</p>
This is a nice technique. What temperature are you using for your soldering iron? Also, what happens if you don't use the oven paper? Does it coat the soldering iron tip with nasty melted plastic?
I have seamed plastic by putting two pieces together, between two very flat pieces of wood. Use portable torch to lightly melt the plastic. Stick the ends out around a quarter inch beyond the wood. The seam is a little thick. A portable plastic sealer, like those used for sealing snack bags might work as well.
<p>Just used this method best one yet so easy and fast. You deserve a gold star. Dilwyn lammas. Also posted method</p>
Do not try it without the oven paper if you are very close to a smoke alarm. You can clean the tip of your soldering iron by pushing it through a cardboard box a few times when it is still smoking :) The iron I use is not adjustable and I have never measured the temperature. If I need to be very careful I fold the oven paper double to reduce the temperature a little.
Melting point of LDPE is 248 deg. F, you don't need to go above that. I just melted a bunch of bags in a pot on my stove. Colin, yes the bags get goopy and if you continue to apply heat, burn and smoke. I don't recommend attempting to make liquid LDPE in your home kitchen. If you do, use the maximum of ventilation.
<p>Hi. just tried the two pieces of wood with material sandwiched tightly in a workmate worked first time. Used very small gas pencil blowgun of Ebay 1,300c. Really strong join, shall use this meathod to make new roof for gazebo, BRILL. Thanks Dilwyn Lammas </p>
<p>It is posible to join transparent vinyl fabric using this technique?, can I use a circuit solder equipment?</p>
<p>Excellent, this was what I needed to apply a plastic liner for a storage unit but none were made for the unit so I made one myself using your instructions. Thank you so much for the info. The unit is now lined with plastic and water resistant. A few hits of silicone at the screw points and all done.</p>
I once used freezer bag plastic, a reconfigured freezer bag sealer and waxed paper like this to make 2 long tubes for sled kite spars. I blew some air in, rolled the tube around a dowel to build up air pressure, pressed a straightedge down to contain the air and sealed it up on the unpressured side. I couldn't believe that I could stand on the tube without popping it ! The rest of the kite was lighter weight garbage bag plastic. The pressure was plenty enough to keep the sled kite in shape. It flew in very light breezes. <br> I made another sled by overlapping plastic from a walmart bag and sealing in 2 places for each spar, leaving a long narrow tube for inflating and rolling up around the dowel. It actually took very little pressure to keep the kite in shape. When I let the reel spin free, the kite went downwind nearly horizontally and shot upward as soon as I stopped letting line out. Some type of reuseable valve could make these saleable.
Just now finished an attempt at making some tubing, and its a good first try! I only used a cut section of one bag wrapped around a paper stick with a layer of parchment inbetween the plastic. So far, its like a fragile drinking straw with a bunch of small holes in it.<br><br>next time, im making it thicker and not applying as much heat. In this case for flexible tubing, possibly, too much heat will make it too stiff and hard.
can you use a wood burning tool
i would think,that if you had a wood burning tool( they are bigger yes?) a thin thin metal cutting blade and some tinkering would allow you to place a roller into the gap at the tip of a wood tool.
pretty much the same thing, you prob. could.
Wow, this is awesome! Thanks so much for your instructable, this is really going to help when I build a garbage bag blimp!
is "oven" paper the same thing as wax paper?
In this context, I would think that &quot;oven paper&quot; would be the same as parchment paper. The difference is that parchment paper is coated with a thin layer of silicon and can withstand the heat of the oven.&nbsp; Waxed paper would melt.<br /> <br /> Suzanne in Orting, WA<br />
an idea just popped! this can be used to extend 2 liter bottles, or can it? submarines any one? or 2 liter-bottle long boat, or better bottle rocket! This plastic welding technique will be perfect for building an inflatable tent that can stay inflated with a computer cooling fan and 9v battery.
Could I use the tip of a clothing iron???
yes you could i always use an iron though you have to be quite careful
Years ago I had a soldering iron that had a teflon coated 'wheel' that replaced the tip (yes, it rolled). It was designed just for this kind of use. ... I wish I knew where I stashed it now!
Thanks for the excellent lesson. I happen to have some baking paper already. Was using if for cooking now I can branch out. zipperboy
Kids in my class are using this technique to build hot air balloons. I've found that the scrap top paper from iron on transfer works like the oven paper and we are using the end of a hi-temp glue gun (new and never used with glue yet)to fuse the plastic sheets. They also have to make a "basket" for an egg to travel in their balloon and return safely to earth. They are having a blast and designing some really cool stuff. Thanks for the good ideas folks.
This works great, thanks! I'm using it to weld 2mm plastic drop cloth with a generic 25W soldering iron and the oven paper. The seams are strong and very difficult to screw up, probably because of how thin this material is.
If you don't have a soldering iron or wax paper, you can use a clothing iron for heat and thin cloth to protect the iron from the plastic.
Can I site you for my next plastic instructable?
Sure! Please post a link to your instructable here when it's ready.
I don't have any Oven paper. So I did a test on a lunch bag.<br/><br/><a rel="nofollow" href="http://img175.imageshack.us/my.php?image=yayzp0.jpg">http://img175.imageshack.us/my.php?image=yayzp0.jpg</a><br/><br/>The thing I used (was harder due to no transparent) Foil. Yup, Normle Foil found in most houses. And I used a High-Temperature glue gun, and ran the nossle on the foil.<br/>
Hey Aleksi, thanks for this. I was able to teach an inflatables Class in Haiti where every student got their own soldering iron + sandpaper kit, it worked like a charm.
i'm also an artist, this is a useful brainstorm page. you might also be interested in learning about the invention of the standard balloon for your own invention process. <br/><br/><a rel="nofollow" href="http://science.enotes.com/how-products-encyclopedia/balloon">http://science.enotes.com/how-products-encyclopedia/balloon</a><br/><br/>i am wondering if a wood burning tool will work as well as the iron mentioned above. if it melts plastic...i don't see why not.<br/><br/>
What kind of plastic bag are you joining? Can you add that to the title or make it a keyword?
I think you can weld any kind of bag. Thick LD plastic (very common in Finland) is easy. The more noisy HD kind is more difficult but still workable. I made a hot air balloon from very thin transparent "freezer bags". Some people even join mylar film this way. Try everything! What would be good keywords?
Unfortunately mylar is not a material that can be heat welded.... I learned this the hard way upon spending countless hours attempting to make it air tight for an inflatable structure I was working on. Mylar is infact a thermoset. It's a really cool material none the less. In case you're curious. I ended up making the structure from PVC discharge tubing which is heat weldable and is inflatable to 60psi. The mylar (since I had a 50ft roll of 4mil and about 20 space blankets) became the skin.
True, mylar cannot be heat welded. Anyway it is still possible to make a <strong>very weak</strong> seam only on one side of the material and it is hard to make it air tight. I guess this has to do with the metallization somehow. For inflatable structures this weak seam would be useless but it should be good enough for a hot air balloon. Anyone had similar results?<br/>This &quot;PVC discharge tubing&quot; sounds useful. What is it used for?<br/>
Hi this technique sounds perfect for what i am trying to create! for my degree show i was wanting to use inflatable black birds. Do you think i could achieve the bird shape using this method? how to fill the shapes with helium do you need to add some sort of device to the balloon? cheers Dawn x
very interesting. I am putting together aerial photography setup, and need to be able to construct my own design helium blimp. Have all the camera, pan and tilt, video and control links already, and am now researching the blimp aspects of it. I want to build something similar to this blimp, but a shape of my own design.
Did you get anywhere with this project?I am interested in doing thesame thing.
Canibul: I'd really like to build a small blimp to carry a Canon S1-IS (offhand, I'd guess it weighs a pound or less). I live next to an extensive marsh and hope to photograph wildlife from the air. I would appreciate any information you can provide. thanks!
Hi Aleksi, hey, this is a great idea! Recently I'm working on inflatables for my design diploma and I thoungt about something like that too. Do you have other expierenence on this topic, or what have you realized so far? cheers from BErlin, Germany, Flo
For sealing, you can use either the old Dazey "Seal A Meal" units-I found one at my local thrift for about four bucks. The only downside is it only will weld a section about eight inches. However, I also got a close look at my crock pot when it failed-there is a big wire inside them that wraps around the crock and heats up to keep the crock warm-you may be able to make a larger unit this way, or a combination welder/foam cutter with one. Again, found at the thrift for cheap. the Vacuum sealer units have a similar heated wire set up. Just some things to try or look at.
This would be a great technique for making solar hot air balloons. If it will handle very thin plastic, such as that used in bags are used to package dry cleaned clothes. In the late '80's I was part of a group that designed and launched a passive solar hot air balloon. It dissapeared from sight within a few minutes and kept rising. If I remember correctly, the tape used to hold the segments of plastic together weighed about a third the weight of the balloon. The lighter a balloon, the smaller it could be made and still fly!
Do you think this technique could be applied to more rubber-like materials, which would normally be under pressure e.g. bicycle inner tube, inflatable RIB or dingy etc... Would the difference in material cause a poor join?
Those are probably thermosetting materials which cannot be melted and re-molded. See the wikipedia articles on <a rel="nofollow" href="http://en.wikipedia.org/wiki/Thermoset">thermoset</a> and <a rel="nofollow" href="http://en.wikipedia.org/wiki/Thermoplastic">thermoplastic</a> materials. The article about <a rel="nofollow" href="http://en.wikipedia.org/wiki/Vulcanization">vulcanization</a> could also be of interest.<br/>
Magic, thanks for that, will be an interesting read : )
Incredible technique!
You can get dedicated heat sealing irons, check out radio controlled airplane model websites can be good sources for info on plastic sheet sealing/shrinking.<br/><br/><a rel="nofollow" href="http://www.modelflight.com.au/accessories_covering_materials_for_models.htm">http://www.modelflight.com.au/accessories_covering_materials_for_models.htm</a><br/>
Awesome, cant wait to try it out!

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