Step 4: Molds

Picture of Molds
You don't need to make a custom mold like I did to make gummy candies. There are many great silicone molds available. They are used for making candies, baking, molding butter, making ice,...

It doesn't have to be made of silicone either. A regular Ice tray will work too. Any thing that has a flat and smooth surface should work fine. I read a suggestion, by a Mom on some recipe site, to pull the rack out of your toaster oven, put a piece of foil on it, and push the foil down through the slats. She made a gummy worm mold that way.

This stuff is very forgiving.

Mold Options

Pour the candy in a flat pan and after it has gelled, then just slice it into squares, rectangles and triangles with a knife. You could cut shapes out with cookie cutters. You could even peel the sheet off in one piece, and cut it up with scissors.

Whatever you do, I'd recommend you keep them pretty small. If you are using an ice tray, or a butter mold, or any mold with large compartments, don't fill it to the top. Just fill them up to around 1/4 or 1/2 an inch.

You can make Mega-Gummies if you really want to. Ever wanted a gummy the size of an Ice Cube? Go ahead. It will work fine. Want one shaped like a Banana? Go ahead - just don't tell me what you plan on doing with it.


I purchased Food Grade Silicone from Douglas & Sturgess. They are a Sculpture Tools, Materials and Supplies store in San Francisco. They are really great folks and have some incredible casting materials that you can't find anywhere else. I bet you MythBusters buys their Ballistics Gel there. Well, I guess I shouldn't bet. Where they bought it is probably on the web, and I've already spent enough money on this project.

The number I used is FGS-2237 Food Grade Silicone. (There is a new number MC-1287) Here is a link

You need two parts. Part A is the silicone gel and part B is the catalyst. They sell it as a set. This is a 1 lb. set.

The silicone must be weighed to make sure you put in the right amount of catalyst. It's 10 parts Silicone (part A) to 1 part Catalyst (part B). Buy yourself a gram scale to do this. You really want to be accurate. You don't want to waste this stuff because you measured wrong.

I made my positive (the part that I made the mold from) out of - you guessed it - Legos!

When I was a kid, way back in the last Century, Legos were still this strange toy from Scandinavia. That was where all the "adult" films and Anita Eckberg came from - she was our Paris Hilton. She was beautiful, classy, spoke with a sultry Swedish accent, and went to the best parties. Well I guess she wasn't very Paris Hiltonish at all.

The only kids who had Legos were the ones who had Moms, or Grandparents, from Europe, or a Dad that we never saw, because he was always "away on business". Those kids got cool gifts. You could tell some of them came from the Airport gift store though.

I had an Erector set and was very happy with it.

Woops Sorry I got sidetracked -


As I was saying, I never had Legos and I still didn't have any when I decided to make this project. I visited the Lego website and found a set that I really wanted that had enough pieces for my mold and bought that. I planned what I needed with the Lego Digital Designer. It's a free software program you can download from Lego and it lets you build Lego stuff in VR. It will even count up the pieces for you and place an order.

I wanted my tray to not waste any space. If I left more than a single peg between each candy piece I'd be wasting the silicone.

When I got the Legos - I built the Taj Mahal - I couldn't resist! Have you seen it? It's amazing. 5,922 pieces.

So three days later, after I finished the Taj, I started taking it apart to get my candy mold pieces.

I put the pieces on a tray, and ringed the tray edge with a double stack of pieces to act as a wall and hold the silicone in (there is a photo of it below). Legos are made so well, that they really fit tightly together. I found that I didn't have to seal any of the cracks between the pieces inside.

Silicone will not stick to Legos. So you don't need to put any kind of mold release on the positive.

Just stick the pieces in there and make sure you stick them down really good.

Weigh the Silicone

To measure how much silicone you are going to need to fill the mold, you can measure it a couple of ways. The standard way is to fill the positive with water, pour the water into the plastic cup you are going to mix it in, and just draw a line on the cup at the water line. That is how much silicone you will need to fill the mold.

You can't let any water get anywhere near your silicone before you cast it though. If you measure your mold with water, make sure you allow plenty of time for it to get bone dry before you try to make your mold.

To avoid the water problem I used Lentils - yeah like in the soup - but dry ones. They have some really small black ones at the bulk food store and they don't put out any dust, so they are great for this. Just pour the lentils over your positive, then pour them into your mixing container. They don't mess your positive up at all. Then you don't have to worry about liquid spoiling your mold.

Put your plastic container - with the line marked on it, on your gram scale and set the scale to zero. That way you won't be weighing your plastic cup, just the silicone. Now pour enough of Part A to get up to your marked line. Don't just glop it in there, try to avoid causing any air pockets. Check to see how much the silicone weighs. Let's say it measured 350g. Because you use 10 parts A and 1 part B, you will need 10% of that weight in Catalyst or 35g. Zero (sometimes the button you use to do this is labeled "Tare") your scale out, with the silicone still on it. Then add the 35g of Part B right into the same container.

Mix it up

Mix your Part A and your Part B with something plastic. The catalyst is blue and the silicone is white so you can tell if you have it mixed. Scrape the sides and bottom as you do it. You want to be careful not to mix any extra air into it. Does that sound familiar? Just like the Gummies!

If you really want to make a perfect mold then you have to "de-air" the silicone. As this involves putting it in a vacuum chamber and most of us don't have one, you can just skip that step. There are lots of tips on the web on how to get the least bubbly silicone castings.

Pour it in your tray

You will pour the mixed silicone over the positive. Fill the tray up until you cover the tops of the pieces.

Pour slowly and don't move the Silicone back and forth like you are drizzling on frosting. That will leave air bubbles in the corners around your pieces. Pour it in a stream that hits the bottom of the tray - not over the Lego pieces, and let it flow around the tray and fill it up. This will help you avoid trapping any air.

Silicone is pretty good about releasing bubbles so you probably will get a pretty good mold.

I'd tap the tray a few times, and I've even held a back massager against it to help it release any air. You need to be very careful, that any of this tapping, or vibrating doesn't loosen any of the pieces inside the mold. I did a test piece and when I was tapping it, one of them floated to the top! I just grabbed my plastic spoon and pushed it back down. The only problem it caused was I wasted silicone, because the inside filled up. Avoid that by making sure your pieces are stuck down really well before you pour in the Silicone.

Let it set up

Don't try to clean up the cup and tools right now. Let them sit overnight. Most of it will set up and you can just peel it off. If you find you have any sticky spots of silicone gel, you can clean those off by dabbing them with a little Catalyst. That will make them set up and you should be able to peel it off.

Let the silicone set at least overnight, then just pull the Legos out of it. They will come out very easily. Let it set up for 24 hours before you use it. I put mine in the oven at 175 degrees for about 15 minutes after it had already been curing for 24 hours, just to make sure. It might not have been the right thing to do (I should have asked Douglas and Sturgess) but I knew they did that with some of the other silicones.

After you get the Legos out, just trim off any of the little bits that squeezed between the pieces. Wash the mold and you are ready to go.

Now if you will excuse me, I have to go rebuild the Taj Mahal.
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Here are a few pictures from my moldmaking process.  The first is the Lego grid I built.  As mentioned on the main comment page I worked the volume out by counting bricks and figuring out the volume.  A 1 lb. container of silicone filled it perfectly.  Incidentally when I mixed it by weight, I had some of the smaller container left over, probably because I didn't scrape out the big container well enough.  The next two pics are just after combining the two parts, and then what it looks like mixed together.  I didn't use anything high tech for this, just a plastic knife.  There were a fair amount of bubbles in the mix, but I ignored them.  When I started pouring the mold, it wasn't moving exactly like I wanted it to.  I did a fair amount of nudging it into place with the knife.  As slow as it is to move, though, it will indeed fill all the voids and level out if you're patient.  You can see some of the larger bubbles in the last picture.  I obsessed over the bubbles, but all the big ones worked themselves out.  There will be some microscopic ones left all over the bottom, but they don't matter.  All of this was done with no prior experience or knowledge except for SFHandyman's instructions, and the mold turned out great.  If you're thinking about trying this instructable out, I urge you to do so.  It's a lot of fun.
Nickname140018 hours ago

you see the little dimples on the side and around the brick moulds? When u fill up the brick moulds u can place the same plate (just without the bricks on it) on top brushed with vegetable oil and the bricks will be build able!

kansas6 years ago
So, so, so, great. Thanks for superb instructions.
SFHandyman (author)  kansas6 years ago
Wow, wow, wow, Thank you.
I have no other reason to get a metric scale. Have you ever made an extra silicone mold and sold them? I know it sounds lazy, trust I'm not that way I just can't justify spending even $5 for a single project then never using it again. I would like to make Lego gummies and ice cubes just for fun.

Lego makes some, actually. The brick-shaped ones aren't always available, but the minifigure-shaped ones tend to be. Plus, if you live near a Lego store, some of them have the brick-shaped molds in stock.


ronmaggi6 years ago
Wouldn't Myth Busters make their Ballistics Gel out of Knox like everyone else?
SFHandyman (author)  ronmaggi5 years ago
I'm pretty sure it's a special mix.
no they said on their show once that they used unflavored gelatin

Knox is a brand of unflavored gelatin. ;) I use it for this stuff all the time.

abbyy ronmaggi5 years ago
They likely use a product that when set, has the density and mass of a human body.

If you live near a Lego store, you can make Lego gummy without having to make your own mold. Their brick- and minifigure-shaped ice cube trays make actual-sized Lego treats for a lot less money than buying the silicone.

But then you don't get to make your own mold yourself. So it's a tradeoff.

deetip20033 years ago
I grew up with Lego, it was and still is my choice of toy for most age groups..myself included lol I can sit and play with it forever. So coming across not only the gummies but the making of the mold also, I was more than excited. The instructions were impeccable, the information on each step was written in such a way that I'd think anyone could understand. I love the way you put your personality into it too. Awesome Job!!!!
skirk34 years ago
is the silicone that was used a soft, medium or firm type of silicone? Appreciate the tutorial, you rock!!
were do you get the mold
These are the best instructions ever, thank you!  :)
Cheezpaper4 years ago
I did this, except I included the inside of the thing so you can build with it. It'd be hard to do it with regular gummies, so I made it firmer.
LEGOs are originally from Denmark (I'm half danish woot woot!)
bsq2phat5 years ago
they do have food grade silicone on their  site, but its under a different number as the website numbers are their own and the ones in the store location is the manufactures... but yeah its at http://www.douglasandsturgess.com/mm5/merchant.mvc?Screen=PROD&Store_Code=DAS&Product_Code=MC-1287&Category_Code= the nuber on the site was mc-1287
zab chev5 years ago
I am currently waiting for the mold to cure..i am so excited!  I am going to make a bunch of these to sell at our elementary school's bake sale.  What kid is going to resist??!!  Have you ever used to molds to make hard candy?  Thinking of doing some of those, too...
SFHandyman (author)  zab chev5 years ago
Woo Hoo, that's exciting.

I haven't tried to make hard candies yet but the silicone I bought should be able to handle it with out any problems. I do have to try it out some day. I'm sure the base plate would melt though so I wouldn't even try that. Just let them be flat backed. I do that usually anyway. It is easier and faster. I don't know how easy it would be to pour the sugar. I wouldn't use any kind of syringe. I haven't played with sugar that much.

If you try it let us know how it works out.
Bruce Koh5 years ago

Really great!!! Thank you.

tajigirl6 years ago
I need help building the taj mahal on the lego download designer. Please let me know the instructions for it. Please thank you
Actually, you can download the building instructions for most sets right from the LEGO website. Go to customer service and click building instructions. Or go here: http://us.service.lego.com/en-US/BuildingInstructions/default.aspx Then search Taj in the keyword search. It will come up with 3 results. They are part 1, 2, and 3 so download them all. They are .pdf and about 10MB each.
LEGO Digital Designer only has a very limited amount of pieces and colors, so you will have a hard time building it according to directions.
SFHandyman (author)  tajigirl6 years ago
That model has 6000 pieces and three books of instructions. I expect the only way to build it is to buy the model.
tatiss156 years ago
hi in the site where you purchased the Food Grade Silicone, send to other countries??? because I'm in Mexico
You can get silicone at a magnificent little store called "Poliformas" (http://poliformasplasticas.com.mx/) there are many of them througout mexico city and all the country. Check their website.
SFHandyman (author)  tatiss156 years ago
I don't know. You have to contact them.
briackman6 years ago
i wonder if you can just cut the bottom off a lego and pour the gummi mix into it? i even wonder if a lego is solid
SFHandyman (author)  briackman6 years ago
The inside of a lego is not lego shaped.
amazing mold putty
This stuff is the best for silicone for beginners. Its food grade... but its about the texture of playdough, and sets up in about 15 minutes.

It says to measure equal amounts of parts a (white) and b (yellow) and knead together until its all the same color, but its very forgiving... eyeballing it works fine and even when one side is obviously a bit off it seems to just make the curing time either shorter of longer but it still forms fine, and is very durable.

They sell it at Michaels as well, near the sculpey and other clays. I really don't get the baby on the cover... it seems like the least likely use most people are going to be grabbing it for of all of their suggested ideas pictured on the packaging.

With something larger like the tray of legos though I think I would probably mix it in about 4 different groups rather than all together... it does set pretty quickly after mixed.
You said "BUT its about the texture of playdough..." is that a bad thing? does it affect the process at all? Have you tried it? :D sorry for all the questions!
SFHandyman (author)  blueraindrop6 years ago
That's interesting. I'll let you know if I "get my hands on some" - literally.
Have you tried the amazing mold putty? I read that someone had suggested it and you said you would try it when you get your hands on it- literally.
headcrab6 years ago
Brilliant made loads of them took them to school (Tech College) and shared them with my friends lol the teacher wanted some
LemonLily6 years ago
This is great for kids, especially the part about making cusom molds. Thank you for sharing this.
Another massive thank-you to SFHandyman!!! You've just given me the perfect idea for how to decorate my friend's birthday cake! Fingers crossed that i'll get it right ... :) Just a quick question to you or anyone in the community: Any recommendations/knowledge of silicone products and/or retailers in the UK (especially Manchester)? Been searching for the ingredients on Google and art-store websites for about an hour now. Almost all the results are US-based. And as for the ones that aren't: I'm too novice to know whether or not they're the right kind. See, it'll be my first time working with ANY of the materials on the list - cept maybe water - and I really don't want to end up poisoning the birthday boy! :S In any case, a million thanks! :) YOU ROCK
Is it possible to melt down solid silicon?
SFHandyman (author)  mouthwashninja6 years ago
No. Silicone is stable at very high temperatures, some above 400 F. There are baking dishes from silicone. Some Platinum Cure Silicones (Like the food safe silicone I'm using) can even be used to cast low melt metals. Casting those pewter figures that the RPG games use can be done in silicone molds.
Astrobar6 years ago
LOVE 'em. So where's the Gummy Taj Mahal? OK, I'd settle for a pic of a couple of these beauts stacked together.
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