Friday, April 27, 2012

How to make one-part Molds

Are you looking to replicate something simple? Is it because you want to make it out of a different material or maybe just because you plan on making more than one? For whatever reason you may need, sometimes molds are just the easier route to go! Depending on the complexity of your object, you may be able to make a one-part mold.

- Silicone or Latex
- Clay (sulfur free recommended)
- Multiple disposeable paintbrushes
- Disposable cups or plastic measuring cups
- Fiberglass resin
- Fiberglass cloth OR
- Plaster bandages
- WD 40 or Mold Release
- Petroleum Jelly
- Scale that can read grams
- Air duster
- Scissors

 Total Cost Estimate: $140
(based off what I had to buy)
Currently Selling For:

Project Duration Estimate: 2-3 days

Many of these materials can be purchased at nearby arts and crafts stores, even Walmart. The actual molding pieces such as the silicones and latexes will probably need to be purchased online.


A lengthy tutorial that will teach you how to make a one-part silicone mold. These molds are often used for simple pieces that have at least one significant FLAT surface that you can use to press against a table with small or insignificant undercuts.

WARNINGS:RESIN of ANY type is extremely dangerous when handled without following proper guidelines. Resin is not only unsafe to touch, but it has a very strong smell and it's vapors will cause very serious damage if inhaled. You MUST work in a well ventilated area AND wear a breathing respirator to filter the harmful airborne chemicals it releases. ALWAYS wear gloves when handling it. If it gets onto your clothing you MUST remove and dispose of the contaminated clothing piece. Do not attempt to use resin if you are under 18 years old. Please ask a parent for help.
LIQUID LATEX may or may not be a harmful substance because latex varies from person to person. Some people are allergic to it and cannot touch, handle, or even smell it, while others can come into contact with it and they will not develop rashes. You should always wear gloves when handling wet liquid latex, wear a respirator, and work in a well ventilated area. Since allergies can arise spontaneously, it's important that you take the extra step to prevent any unneccessary contact.

SILICONE can often be dangerous if handled without gloves. Many mold silicones are unsafe for prolonged skin contact and should not be handled for long periods of time or be allowed to dry on the skin. Some types of silicone also often release very strong smells. While some of the fumes are not dangerous, they are very unpleasant. Please wear gloves and work in a well ventilated area.
AIR DUSTER is a very dangerous cocktail of chemicals and is NOT to ever be ingested or inhaled. When using a can of air duster, aim away from your or anyone else's face. It also often releases freezing air which is very painful.
ALWAYS read the warning labels on products you are unfamiliar with.

Always make sure you read through the entire process before beginning to avoid mistakes and get a general idea of how the project will progress.
Now let's make get started:

Step 1: Preparing your Subject
The very first step in this tutorial is going to be finding and preparing the piece you're going to be molding. If you're piece is already made and ready to go, then skip this paragraph. If not, then I can only assume you're sculpting or making the piece yourself. Generally, when making an object you want to mold, it's popular and useful to make it out of air-dry modeling clay (water based). You can go with oil based, but water based is just easier to clean. Anyway, when you sculpt your piece, make sure one of the surfaces is completely flat and will not be difficult to remove the silicone from. I used a couple sheets of wax paper to keep the silicone from making contact with my table. Generally, you can use a piece of wood or a plastic table, just make sure you don't care much for it. To make the piece flat, simply work on a table and press the bottom surface flat against it. If you're doing an intricate pattern such as I did, you're probably going to want to make the indents very deep so that the silicone that gets into any of the crevices is strong and thick enough that it won't break off. Once it's done, let it dry off completely. If you need to take breaks from working, simply put a bit of water over the top of the piece and wrap some foil over the top so it won't dry out.
Now that your piece is done (or you already had one) you need to make sure the bottom piece that is flat against the table doesn't allow air underneath. If you sculpted it against the table as mentioned, then it shouldn't be too big of a deal and you can probably skip this step.
However, you will need to spray MOLD RELEASE onto your piece regardless of what it's made of! Home Depot usually sells a universal mold release. If not, Michaels, AC Moore, and other craft stores often sell mold releases, but they're often way overpriced.

Step 2: Coating in Silicone
Now that you have the piece ready to go, we're going to coat it in silicone. For this tutorial, I used Mold Max 30 (it can be found here) as well as Thi-Vex, a thickening agent (found here). You can use other things, I simply used Mold Max because it was recommended to me. Even if you don't use Mold Max, most molding silicones are very similar, so you should be able to still follow the tutorial. Anyway, the first thing you want to do is measure out your contents accurately. For most silicones, you have a part A and a part B that you need to mix together to a certain ratio. Mold Max is a 10:1 ratio respectively A to B. This means 10 parts A for every 1 part B. For a more detailed explanation, view the video here. Anyhow, once you've got the silicone mixed, you're going to need to put on a thin first layer of silicone. Simply pour your silicone onto the center of your piece and use a disposable paintbrush to lightly work the silicone evenly all over your piece. This layer is very important because it will capture all the detail of your piece. Don't use TOO much silicone, it'll just run off the piece and onto the surface of your table, just use a light layer. Once your entire subject is coated with a decent layer of silicone, take out your air duster. You'll need to lightly spray the surface of your piece to reveal and get rid of any trapped air bubbles that may have formed. You DEFINITELY don't want bubbles in the piece or you''ll get unwanted bumps and lumps in your final cast. The bubbles are a bit difficult to spot, but don't be scared of the weird shapes that form when you spray the air at the silicone. Here is a nice video showing the process.
Once the first layer of silicone is on, allow it to semi-dry for an hour or so before you add your second layer. Adding the second layer is the same as the first, you SHOULD use the air duster to reveal and get rid of any air  bubbles. Depending on how runny your silicone is, you may or may not have to do this the other later layers. If your silicone is very runny, almost watery, you may want to do it again. If an air bubble gets trapped right under the surface of the mold, there is a chance it may tear open when you de-mold anything from it and you certainly don't want that. Anyway, once you've added about 3-4 thin layers, it's time to take out your Thi-Vex or other thickening agent and add it into your next batch of silicone. The thickening agent is great because it will add strength and multiple layers to your mold. It's a quick way of bulking it up and you want it to be relatively thick or it will be more prone to tearing. Not only this, but thickeners are often vital depending on your piece. If your subject has lots of undercuts, you need to fill them with silicone and slope them so that your shell won't snag onto them and tear them off when demolding. If you're confused as to what I just said, just make sure you're finished silicone piece looks somewhat like a dome. You want all the edges to be smooth and you want the bottom to be wider than the top. In the next step, we will make a shell and if the shell can get under anything in your piece, it's no good. Use the silicone thickener to get a cake icing thickness of silicone that will stay put so you can fill any spaces with it. Silicone thickener generally doesn't have a ratio to be mixed, you simply add more the thicker you want the silicone. For my mold, I put 3 thin layers and 2 thick layers.
Once you're done, let the mold rest and cure overnight (roughly 16 hours).

Using Silicone Caulk
If you're going to be using silicone caulk, things will be a bit different. It's supposedly bad for you when it comes to frequent skin contact. What this tutorial calls for requires handling the caulk directly and I've been told that it's not harmful so long as there is no prolonged contact. If you don't want to handle the silicone, simply wear some gloves or use a tool rather than your hands. If you do handle the silicone, make sure you wash your hands thoroughly after use for about 5 minutes to completely dissolve any remaining silicone. Besides that, work in a well ventilated area, this stuff reeks.
Anyhow, the very first layer should be thin and carefully done since it's the one that will be capturing all the detail. Once you've got it done, you can add more on top. To apply the silicone caulk, you're going to need a caulk gun and a cup of soapy water. Caulk guns can be bought in the same area as caulk tubes, so just grab one when you get your tubes. To make your soapy water, put a super load of soap into a cup and jet in some warm sink water. The soapy water is used to keep the silicone from sticking to your hands and it works quite well. Add a nice glob of caulk on one side of your piece and use your fingers to press it across the entire length of the piece. If you need to add more caulk, add it over the caulk you already have set. This prevents air bubbles from getting trapped. Push the caulk into all the crevices, adding any more that you may need to fill them. Caulk dries rather quick, only about an hour or so, but you don't really need to wait for it to dry inbetween layers. Once you've got one layer of caulk across your piece, let it sit until it gets a little gummy, then just add some more on top. You shouldn't let the caulk dry completely, as silicone sometimes won't stick to itself once cured.

Using Latex
If you're using latex, you generally will do the same as the above materials, however, you will probably be working in much thinner layers. Mold making latex is essentially liquid latex. Whereas most silicones are runny but have a more paste-like consistency, latex is VERY runny. Do the same as you would with regular silicone, adding a small layer first to capture detail, then work yourself up with multiple layers. The advantage to latex is that it dries VERY quickly, so time inbetween layers shouldn't be that bad. Since latex is so runny, your first layer will probably be VERY thin. Simply add 3 or 4 layers in this thin latex just to ensure you can SEE that there are no bubbles. Once you've done the first few, you can use latex thickener to thicken the latex and pour it on top, saving time.

Step 3: Making the Shell
Now to make the support shell that will go around your mold. This is important to have because it keeps the silicone from flopping around or sagging when you're making a cast. You don't want a warped piece do you? Anyway, you can make the shell multiple ways. Most people will go with plaster bandages because it's cheap and simple, but they tend to release lots of debris overtime and are a bit weak. You can also use plaster of paris or other plasters, but they are often very bulky and hard to store. I used fiberglass sheets and fiberglass resin to make a lightweight, thin, yet durable shell. The downside, however, is that fiberglass is gross and smelly. Fiberglass cloth is ok to touch, but when cut, it makes a mess, and resin smells horrible and is bad for you, so working outdoors in a well-ventilated area is always a good idea. You WILL NEED GLOVES. I don't care how awesome you think you are, you WILL get resin on your hands and it will be unpleasant. Anyhow, the first step no matter what you use, is to take a knife and trim the excess silicone around the mold. Keep about an inch or so around the actual piece. Next, coat the silicone in petroleum jelly. The jelly can be found in any drugstore or a regular store like Walmart or Target. Simply grab a brush or use your hands to spread a very thin coat over the top. If you want to, you can also add a layer of WD40 just for good measure. Let it dry for a few minutes. If you're going to use plaster bandages, simply grab a bucket of water, cut them up, dip them in the water and apply them to the surface or your piece. If you're using plaster of paris, add some water to the powder, mix it up, and coat a large amount onto the surface. 
If you're going to be using the fiberglass, cut all the cloth into strips first. Once you get the resin onto your hands, you won't be able to stop and cut any more strips so you may as well just cut it all beforehand. Not only that, but resin has a very short working time so you won't have any time. It's easier to just grab the strips of fiberglass and throw them onto your mold and never touch them again. They're going to come apart and annoy you soon anyway. So once you've got them all cut up, mix your resin with the catalyst and grab another paintbrush. Lay a strip of fiberglass onto the cloth and dap it with a nice amount of resin to stick it onto the mold. Since you added the petroleum jelly, it will be a little difficult, but just dab the paintbrush downward directly onto the cloth rather than stroking it sideways to keep it from moving very much. Simple as that, just keep adding the cloth until you have about 2 layers of it, then let it dry completely before removing it.

Step 4: Demolding
Finally, the most exciting part! Now it's time to detatch your mold from the table, take off your shell and remove the inside to look at your mold! First things first, remove your shell, this should be relatively easy since we added the jelly to lubricate the surface. Now, gently peel the silicone off the surface. Depending on what sort of piece you have, this may also peel the silicone off the original piece. If not, just get ready to flip it over and fight it off. Now you're probably regretting the fact you put all the jelly on the surface, at least I did. The silicone was really gross to touch because it was so slimy, so maybe put some gloves on for this part. If you're like me and you used a clay sculpt, you will probably end up flipping the mold over and tearing it out. Don't be too forceful, but if you need to, you can stretch the silicone to help remove any complex pieces. Once the majority of the clay is out, you will probably see a destroyed original. Unfortunately, this is inevitable unless you completely massacred the original piece with all sorts of lubricants. Either way, there will probably be some residue inside the mold as well. This is a great advantage to using water based clay, all you have to do is dunk your silicone piece into some warm water for a few minutes to dissolve the clay and rub any remaining chunks off with your finger. If you're like me and you used oil based clay, you can also put it in warm water, but this will only loosen the clay. You will probably need to scrub it off using a soft scrub or a toothbrush as rubbing it with your finger will only spread it around in a thin layer. Once you remove all the clay, you may notice some rough edges or extra silicone in your mold in very thin feathery layers. These are little layers of silicone that manage to get under raised surfaces. Simply grab some scissors and gently trim any excess or unwanted silicone to clean up your mold.

A lovely one part mold that you can use to make many copies of that lovely sculpture you had to sacrifice!

For more information on purchasing jewelery and other props in my tutorials, requesting a custom item, or an idea for a new tutorial, feel free to email me at Kanti-Kane@hotmail.com (: 


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