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Make a silicone mold from common household materials in your kitchen in 1 hour

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Taking off from this BRILLIANT 'ible http://www.instructables.com/id/How-To-Make-Your-Own-Sugru-Substitute/ I have started making silicone molds on the cheap and thought I would share. This is incredibly simple and fast and can be used for a ton of casting ideas...

Here is the podcast I did on it:


The basic instructions are below....
 
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Step 1: Materials

Picture of Materials

You will need:
  • SIlicone Calking (the stuff that stinks like vinegar or acetic acid) I have a calking gun but you can get smaller tubes of it at the hardware store
  • Mineral Spirits (this is just paint thinner but somewhat less toxic than the rest. NOTE: you can use white gas or camp stove fuel but be CAREFUL if you do use that. The advantage of white gas is that it will cure the mold faster and the mold will not smell like mineral spirits after)
  • Corn Starch
  • Vaseline
  • Latex gloves (or what ever kind you like)
  • mixing sticks
  • Drill
  • Bent nail
  • Something to cast or mold
  • Small box
  • Mixing cups
  • Wax paper
  • Play dough

Step 2: Prep the item to mold

  • To prep the item for the mold cover it with Vaseline (if it is a bit goopey use a blow dryer to melt the Vaseline and smooth things out).
  •  
  • Next cut the bottom of the box out and place it on a piece of wax paper
  • Get some play dough and fill the bottom of the box with a layer thick enough to cover half the figurine (don't put the figurine in yet this is just setting up the base
  • Press the figurine into the dough and make sure to cover 1/2 of the figure
  • Vaseline the dough and the figure (if it is a bit goopey use a blow dryer to melt the Vaseline and smooth things out).
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C Diane2 months ago

I tried using 50/50 silicone and cornstarch since I wanted a more clay-like consistency to mold over an object. The stuff never dried and had to throw the whole thing away. I used GE premium waterproof silicone for kitchen/bath/plumbing (100% silicone and regular corn starch. What did I do wrong?

ge silicone is different and will not cure the same with corn starch. you need to use regular silicone that smells like acid.
Rossana672 months ago

I read that aquarium rtv is food save. If I use this silicone, can I make molds for cake decorations?

JestGold7 months ago
Will be trying this to cast some 5" square tiles in hydraulic cement. From what I've been reading in the comments in Mikey 77's great post, using naphtha thins the oogoo and does not give off odors once cured, as compared to using mineral spirits or paint thinner (evidently these continue to stink well after the oogoo is cured).

I think I will try thinning the silicone with the naphtha before adding the corn starch. If anyone has done this, I'd love to hear about your results. But I will try for myself.

Thanks for a great post, and video, which really helps to see what's in store for me.
I love it!!!!! Works great. Im using Naptha.
Thank you for sharing
MechanicalMashup (author) 11 months ago
I am thinking you need to add less cornstarch and add it last... This might sound odd but do you live in a humid environment? The more humid the less cornstarch as the cornstarch pulls water from the air to set off the silicone. If your in a humid area the there will be more water in the air thus set the silicone off early.

Experiment a little.
spider8711 months ago
Not a single person has has the same experience? Lol
spider8711 months ago
I don't understand what I'm doing wrong.. I tried 50/50 then a healthy portion of mineral spirits then I tried 4pts corn starch 8pts silicone. However, when I add the spirits, everything starts setting up right away instead of softening.. What's going on? I'm mixing with a knife not a power tool.. Could that be it?
thomas966611 months ago
Thank you so much, been looking for an easier and cheaper way to cast molds for a long time
jhante1 year ago
Very nice instructable! I work in the industry, my company makes prototypes by casting and other methods, so I was interested to see how it can be done in your kitchen!
owsamphoto1 year ago
Could I used the mold in fondant cake designs? Is it safe or food grdae
gemini17201 year ago
http://www.makeyourownmolds.com/how-to-make-molds

check out the link for food safe mold making for cake decorating mold making
dlrlt5301 year ago
Does anyone have a silicone recipe that IS safe for food and can be put in the oven, safe up to 500 degrees? Or is there such a product already out on the market? I need it in liquid form, so I can make my own mold.
binkibow1 year ago
Hi I'm in the UK & cant find 'Silicone calking' any idea what else it may be called here ?? I have been asking & retailers look at me blankly.

Cheers
the silicone calking it´s the silicone in the tues using for bathrooms, fish tanks , seel window gaps, in portugal we can get it in drog stores, i think that in ingland is the same
Silcon sealant is the same, or bath seal. You can get it in any diy store
MechanicalMashup (author)  binkibow1 year ago
Did a little research and they should not be giving you blanks stares...
http://www.google.ca/search?hl=en&safe=images&client=safari&sa=X&ei=5qYvULHtPKOKjAKC3oCwCg&ved=0CFcQvwUoAQ&q=silicone+caulking+in+the+uk&spell=1&biw=320&bih=417

Maybe try asking for bathtub sealant. Sorry that's the best I can offer.
MrRetardo1 year ago
I've used Silicone Caulking to make molds before. For thicker molds, mix in some Glycerin. It helps the silicone cure in thicker layers, as silicone caulk cures by reacting with moisture in the air.. For a release agent (keeps silicone from sticking), try using a silicone-based spray such as Armor-All.
Hi, I am in need of molds for my project (it will be on instructable once I manage to finish it). I need a mold that has a minimal shrinkage. (IE 1% max). I am going to try the glycerine (I found a bottle at my local drugstore). I was wondering if I could add talc instead or starch? Anyway I think that 10:1 by weight for the silicone glycerine mix would work ok. I'll try and give you news.
Corn starch only it's hydrophilic. This is what sets the silicone off faster. Talc will not do that. Glycerin will also help set the silicone off and thin it but I have not experimented much with it. So make a couple batches and then after a week measure shrinkage.
I have failled miserably. Going to wait and buy the smooth-on kits ;)
halo993 years ago
Would this also be safe to use with food molds? (jello) would it be eatable?
MechanicalMashup (author)  halo993 years ago
NO!!! sorry this is far from safe for that.

I would imagine that if you got food grade silicone from a hardware store and only used cornstarch that it would be safe but I am not sure it would be pourable or as manageable as the video shows.

So I say again NO it is not safe for food as is but the above suggestion may make a mold that is usable. I am no expert in this though and you are on your own if you want to experiment with that...

Dont think I am being negative or being a jerk, far from that, we love our fans. I am just being concerned about your health an like our fans to be healthy and alive :) Otherwise they don't promote us nearly as well, last I checked there is no internet connection to the afterlife...
Food grade silicone, glycerine and corn starch.
oh ok thanks
See this link for food grade silicon: http://www.smooth-on.com/Silicone-Rubber-an/c2_1115_1131/index.html

I have used it many times with great results. If you look at my sugar glass 'ible http://www.instructables.com/id/Sugar-Glass/ you'll see my bottle mold in the pics. I have used it to make chocolate bottles, also.
neodymium2 years ago
Could I use a non-alcohol thinner like turpatinen or a low alhol content thinglike 70% rubbing alcohol? What would happen to the mix if I didn't add any at all, because it sounds like it would shring less without any thinner? Thanks.
Anyakin2 years ago
This is why I love Instructables :)
kommodore2 years ago
Dude!!!!!!! i just try this and it turned out excellent!!!!!! thanks for this great instructable!! i was wanting to make some silicone mold for a long time, and i didnt wanted to spend like 40 dollars on 1 kg of two part rubber silicone, so you save me a lot of money, i mixed silicone and corn starch on 1:1 ratio, and then add paint thinner, the mold turns out really well, alltough, next time i will use some more paint thinner so the mix gets more runny.

So thank you!!
mschell12 years ago
if you dont add the mineral spirits, does the mold still shrink?
MechanicalMashup (author)  mschell12 years ago
With no mineral spirits the mold will stink but very very little compared to a mix with mineral spirits. With glycerin it will stink but more than no additive and less than mineral spirits...
I bought odorless mineral spirits in the art section in Michaels. It's by the brushes, oils, canvases, etc. I don't think I added enough and my mold is lumpy but it got the job done. Ugly as all get out tho.
MechanicalMashup (author)  mschell12 years ago
Glycerine does not thin as well as mineral spirits but definately does not smell nearly as bad. Remember that when the silicone kicks it will smell very strongly if vinegar or acetic acid...
cathypeek2 years ago
I want to make triangle shape crayons from melting old wax crayons. Is it possible to pour hot crayon wax into this type of mold?
Also im going to be making a shed-load of molds for pouring casting-resin into (potting) and the resin cures by a chemical reaction causing the tepmerature to rise to about 60°c (140°F) and will be using a silicone caulk thats rated to be temperature resistant to upto 300°c (572°F !!!) !

The one i bought is called 'Heat Mate' in the UK (bought from my fav specialist shop, ebay, lol !)

Plus im going to be using this heat-resistant silicone to make some RC Buggy Parts that are located next to the engine so that it can better protect against a very high heat source !!!

Hope that helps !
Thanks offtherail2010! I appreciate the Heat Mate silicone caulk tip. I have made a mold--you should see it...pitiful but it's a triangle-shaped mold. I took leftover crayons home from school to melt and those crazy things would NOT melt! Oven at 300 degree F. They must have plastic in them rather than wax. Need to buy the old crayola brand and I bet they would melt. This is my goal over the summer. Have a great week!
Your most-welcome cathypeek !!

Always happy to help !

lol @ pitiful !

As long as your mold serves its purpose i always say it doesnt need to win any beauty-contests as long as it does what you need it to do lol x 2!

Also with repetition you will get much better at creating molds as after the 1st one its all a learning curve & the good ol' trial & error methods !

Just slightly curious thought, is there a specific purpose for having triangular crayons ?!?
MechanicalMashup (author)  cathypeek2 years ago
Yes it is... The temp of the crayons melted is fine with these molds
Thanks for your reply. Realized I needed a 3D triangle shape so I purchased sculptey clay to make it. I am going to try making a mold but need to watch the video again. I'll let you know how it goes. Thanks again!
*** !!! DUDE !!! ***

I'm back to finally test out your GREAT instructable !!!

i just have a question whilst i wait delivery of some Play dough !

Instead of using mineral spirits, would you think it'll be a good idea to use 99.9% Isopropanol as its the closest thing i have to any kind of spirits ??!!!??
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