Step 3: Mix it Up !

Now that you have gathered all the necessary materials and ingredients, its time to mix up a batch of potato plastic. A note to younger viewers: be sure to have a parent with you when using the stove, I don't want you to burn down your house because of this instructable! Also, beware of the starch plastic resin when you are pouring it into a mold, it is very hot and will burn you if it gets on your skin, you can never be too cautious with boiling hot substances.

1) Measure out 60 ml (4 tablespoons) of cold water and pour it into the beaker or container your heating the mixture in.
2) Measure out 10 grams (or about 1 tablespoon) of starch ( the potato / corn starch you made or bought) and add that to the water.
3) Add 5 ml or about 1 teaspoon of acid (vinegar) to the mixture.
4) Add 5 ml or about 1 teaspoon of glycerin to the mixture, more glycerin will make it softer and more flexible, less will make it harder and stiffer but more brittle.
5) If a colored plastic is desired, add in the food coloring now. About 5 drops is good enough.
6) Turn the burner on low and constantly stir the mixture. When it starts to thicken up turn the heat up to medium and stir even more. When it starts to boil, keep boiling it for 5 minutes. You want it to be very clear and sticky (not like toothpaste though, think flubber)
7) You should now have a "gooey" substance that you can pour into a mold, or you can pour it onto a sheet of aluminum foil/silicone heat pad to dry.
8) Depending on humidity, it should take about 1 day to dry in a sunny place. You can dry it faster by putting it in an oven set to 150 F for 1-2 hours.

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agracia12 years ago
This would really help us on our science investigatory project.But can we use banana starch instead of potato starch? And what other chemicals can we use instead of making a schweizer's reagent?

This is interesting and I really need your help. Can i get a copy of the research paper of this ?

MisMo4 years ago
Hello Lupe!

I am wondering if you could send me your research paper as well. I am trying to reinforce my potato plastic as well, so far in vain.

Thank you so much and keep up the awesome work!
lupefiasco5 years ago
Hi, I'm doing a research project, where I'm reinforcing these plastics with natural fibers, and entering a contest with it. However, I'm having great results with reinforcement, but without it (what you are doing here), my plastics are not drying, and are still gooey after a month. I have dried the other plastics by pressing them between two glass plates, because I need a smooth surface as I am testing them with a tensile tester. I have followed your recipe perfectly in terms of materials, but could you give me some more specific temperatures in Farenheit, of what you consider "low" and "high" temperature? I think that this may be the problem. Thanks, I would really appreciate an expedient response. (
helo, lupefiasco, wat kind of natural fibers tat u add on ?my plastic is too soft and tear off when juz touching it...I wan to test my plastic on tensile test too, but it is too soft and cannot be tested by machine... do u hv the same problem as i had ?
Hi there,
You may be adding too much plasticizer, or you may just need to spread the plastic thicker. Experiment with types of plasticizer, because that will dictate those kinds of properties. I use cotton, jute, and hemp fibers in my study, and hemp performed the highest in resisting water degradation as well as in strength tests. I will share my methods with you here, feel free to ask if you have more questions.

"Phase I of the experiment involved the creation of samples for testing. A slurry of 2 tablespoons of starch and 8 teaspoons of water was created. If applicable, 6g of fiber was added and mixed into the slurry until it became relatively homogenized. Then 1 teaspoon each of glycerin and vinegar were added to the slurry. The slurry was heated at low on an electric stove, then when it began to steam, turned up to high and allowed to boil. Then the slurry was poured and spread onto two glass plates with non-stick surfaces. The plates were then pressed together to create a flat layer of plastic. This process was repeated for each fiber, and for the control plastic without fiber. After the plastic had partially solidified, one glass plate was removed and the plastic allowed to air dry until completely solidified."

"The results of the tensile testing supported the hypothesis that the hemp fiber reinforced plastic would demonstrate the greatest tensile strength. The reinforced plastic had an average tensile stress at break of 2138.63 psi. A Kruskal-Wallis test, which compares the differences among medians, conducted on the tensile strengths of hemp, jute, and cotton, and non-reinforced (control) plastics showed that the differences are statistically significant (k=10.3846, p.= 0.016).  As shown in Figure 5, the hemp-reinforced plastic was significantly stronger than the other plastics. The fiber-reinforced plastics were also significantly stronger than the non-reinforced control. As shown in Figure 6, though the hemp plastic failed quickly under tensile stress, it was a brittle failure, and the plastic held a large load."

So since the plastics suffered brittle failure, the problem was the plasticizer, and I suspect that you are having the same problems. Following these methods you should be able to create plastics that stay together and are strong.

thx 4 yor info....i hope u dont mind if i hv questions to ask u...haha...anyway, thx 4 for yor guide and tips....i'll try my best... ;)
 Sure thing, let me know. I can't promise I can tell you everything, I haven't worked on this topic for a while, so it's a little hazy. I hope to pick it up again this year though!
Hi, more long time does the (gel looks plastic)plastic takes to solidify as a real plastic (dry and hard plastic ) after u put the plastic on the flat plate ?
Less than 24 hours for me.
Brandon121233 (author)  lupefiasco4 years ago
 Awesome! Finally a comment posted above the average elementary school intelligence level. Lupe if you publish a paper on this when your done would you mind sending me a copy? 
 Hey there, I've actually been long done with this project. I did well with it at state competitions in 2009, but I changed my focus to the biological aspect of plasticizers this year. I do have a copy of the paper, where would you like it sent?
Brandon121233 (author)  lupefiasco4 years ago      thanks, I'll let you know what I think about it, its always good to see other peoples ideas on the same topic 
Brandon121233 (author)  lupefiasco5 years ago
I have never really taken accurate measurements with a thermometer, just because its easier for me to just look at it and know its done. The starch changes dramatically in appearance when its done, from a gooey paste to a bubbly and very clear gel thats very sticky (look at the video to see what I mean). Sorry I can't help you more with that
iv_tch008174 years ago
helo brandon, my experiment juz stop at 1.53 ( the specimen like toothpaste look )....when i continue to burn it, it dries out and it doesnt looks like gel...what is going wrong ?
Hey brandon,i want to ask whether we can replace the vegetable-liquid glycerin with other substances? cause i'm from singapore and vegetable-liquid glycerin is not readily available.
Drugstores sell glycerin
Brandon121233 (author)  angelicgirl19955 years ago
try sorbitol
continuing the substitution possibilities, as both sorbitol and glycerine are a little hard to find...

could you use sorbitol chewing gum?  Maybe chew the gum 10-15 seconds and spit out the juice?

Are there soap brands that are almost pure glycerine?  Dish detergent?

Other recipes here use a lot more starch, but with vegetable oil.  Is the main reason that: Glycerine saves money if you are making a lot? Or its a lot better quality?
can you make plastics with other substances (other then: potatoes, petroleum, and corn)?
blah225 years ago
ahh. ? good. very good. huh?!
matchett8085 years ago
hmmm....on the commercial side of it a few months wouldn't me a long enough lifespan....try adding some anti-bacterial agents (or just spray some detol in! lol) Interesting thing is that if you where to combine this with a small amount of petroleum plastic then it would increase the strength and increase the lifespan too! Is this a thermosetting or (other)? (lol - i canny mind what the other is called) From one of my old jobs have you tried heating and cooling the mixture at step 6 or 8?? thermocycling can have different effects on different polymer chains.... ...What acutally is the strength of this plastic is it comparable to petroleum based plastics?
bac5125 years ago
does this make CLEAR plastic? If not, is there any way to make it clear?
Dayi5 years ago
Thanks Brandon.... Well now I have an other question :b I didn't really get how to do the starch!! How can I do it??? Is there an other way or can I do it with an other type of starch???
mimiu785 years ago
wow this wil help a lot, thanks! i have a question regarding the molecular structure of plastics, i've read the last page, but are all plastics linear? or are some branched? I'm trying to find out what the difference between plastics, and other polymers..
Dayi5 years ago
Hi Brandon I really liked this of making potato plastic... I tried to do it but I don't know what Im doing wrong because it doesn't look like yours.... I didn't use 100% Vegetable Liquid Glycerin I used normal Glycerin, was that the problem??? I also used an other type of starch. When I'm mixing it, it starts getting like gel but it never turns to plastic :( Do you know what I'm doing wrong?? help please.
Brandon121233 (author)  Dayi5 years ago
different types of starches behave differently, I would add about 10% more water and cook it longer and hotter
enaile5 years ago
hi! i tried to do this project but used starch extracted from the peelings of potato, orange, and carrot instead. i followed the instructions but it doesn't end up the way yours did.while i was heating it, it dried quickly and i added water.when it was klinda gooey, i poured it onto the piece of foil but its not yet has been five days.i need help.what do you think is the problem? i'm also wondering if i could use pure glycerin instead of the vegetable can email me at
marais_kris5 years ago
very cool instructable......... I was just wondering, uhhhm, will animals eat the plastic, well, because, it smells like food!! Sori 4 the weird question, hey, I'm just curious, I'm only a kid!!!!
justineqt6 years ago
first of all... nice instructable.. this is very creative... _

ahmm.. i actually have a question, i have seen on the comments that one should use baking soda.. and i have no question why... ahmm.. i would just like to know how many mL/teaspoon of baking soda must be used? or the ratio of the baking soda and the vinegar? thanks a lot..
Brandon121233 (author)  justineqt6 years ago
actually the whole point of the baking soda was to neutralize the acid of the vinegar (I previously thought that might damage the plastic over time) however I have observed that theres little or no degradation f the plastic with or without neutralized acid in it. That being said, don't worry about it just follow the instructions in the video.
xiansz096 years ago
cool! this is helpful.. :) do you really need the glycerin though? i'm planning to make this for our science project... so if you can, please reply ASAP ty... :))
fishing kid6 years ago
So if you add more glycerin it will become softer? And if you add less glycerin it will be harder? I'm trying to make some soft plastic swim baits, and possibly some lures. And I was wondering if I could use this recipe to do so.
mymy6 years ago
hello, i would like to use this procedure in my investigatory projecty but i am curious of why did u use baking soda?? what is its purpose??
This is totally awesome, is the vegetable glycerin the plasticiser? if so what are the quantities needed to have the wide range of soft to hard plastics?
misslisa7 years ago
Super Cool!!! Brandon, need help . . . when I make the plastic it ends up as one big blob and hard to separate into small blobs. I am trying to mold small (nickel size) game pieces, and would love it if the plastic were more "pourable" or a softer liquid-solid consistency. Any thoughts???? Thanks mucho!!
Brandon121233 (author)  misslisa7 years ago
Try using a bit more water, and also start it on a low heat and very gradually raise the temp. up to med-high, then right as it starts to go clear and jelly like, boil it for 1 more minute, then QUICKLY before it cools pour it into the mold. As soon as it starts to cool, it will glob up and stick together instead of pouring. Hope that helps...
Brandon121233 (author) 7 years ago
Depends on what you plan on shooting with it, and if you want it to last multiple times... I doubt that a projectile made with this would last if it was used to shoot a tree or car...but it would do some heavy dammage