In my quest to learn how to prototype great products, and share my discoveries with you in the process, I got interested in clay and moldable plastics for prototyping. I spend the last weeks comparing each types of clays and brands to make the most informed choice before to start my project.

Clay is great for prototyping because it’s quick and easy to use, it’s versatile and cheap, and a pleasure to play with.

I have been playing with clay for a while. I learnt how to sculpt and fire traditional clay when I was a kid, and even took my potter’s wheel with me in my student room under the roof in Paris for playing after school. During my research, I was very happy to discover so many new innovative clay-like materials available. It’s pretty inspiring.

Plenty of advanced clay materials with special properties might come in handy while prototyping your product. The goal of this article is to detail different ways of using clay for prototyping, show you different types of clays and moldable materials that are useful for prototyping and pick the best product for each type of prototyping need. See it as a buyer’s guide to find the best clay for your prototyping project.

Go all the way to the end if you want to know the winners for each category and skip all the (valuable) content.

Clay is not only for sculptors, kids and crafty mums. It offers a wide range of possibilities for product designers and inventors, from quick drafts to moulds making to making actual products.

Clay can be used for prototyping in at least 4 ways:

1. Making your idea concrete in a few minutes. Quickly sculpting a first shape of your idea is a great addition to sketching or describing it in a notebook. You get to instantly visualize how it could roughly looks like… and remake it over and over again until you are ready for the next phase.

2. Getting faster to the 3D modelling phase. Once you made your clay model, 3D scan it and you’ll get a pretty accurate 3D model to work from. An accurate and well-finished clay model will also be of great help for presentations, team demos and tests.

3. Making a mould that can be used for casting your prototype and producing a small serie of your idea. Clay moulds are also great for making multiple parts faster and adding specific textures to your prototype.

4. Adding parts to an existing product or prototype, or connecting multiple parts. Clay is a great connector between pieces. Keep it in mind for adding new features to a product or testing a waterproof piece.

1. Quick sculpting

First, let’s say you want to create a quick visualization of an idea you just got. Maybe you drew a few sketches in a notebook already, maybe you wrote down your idea to remember it and start iterating on it. Using clay at this early stage is a great idea because it will give you an instant concrete feeling about your project. While sculpting the shape you have in mind, you will realize challenges to come, questions you haven’t thought about yet, and you will have a first draft to work from.

Some inventors prefer to use cardboard, toothpicks and glue to create quick prototypes. It works too, but getting some cheap clay that never dries and can be used multiple times will be a great addition to your prototyping toolbox and might even become your number one prototyping material.

Industrial design clays for prototyping

Traditional clay – the one used to make ceramics – is a mineral, which usually mixes organic and metallic materials found in the earth. It’s a material filled with water. When water evaporates, mineral clay dries and becomes more and more sturdy. Once fired in a high temperature oven, it hardens and its chemical composition changes for good. It can then be used for potteries, bricks, decoration items, floor tiles… and industrial design. Industrial design clay comes in beautiful white, gray or brown color.

Mineral clay can be used for quick prototyping. It’s easy to shape and soft. You have plenty of tools available to sculpt it the way you want, and you just have to use water in a little bowl near you to keep it wet and sticky. I would not fully recommend it for this kind of quick use though because it can be pretty messy. Mineral clay tends to stain and stick to your hands and desk, you will quickly end up with brown drops of water all around you and will need to wash your hands and protect your clothes. Not the best if you are working with your computer and is busy doing other things than sculpting, like I do.

If you’re interested to give it a try anyway (it’s really a lot of fun), I recommend professional-grade Chavant DaVinci or the cheaper AMACO that sells a block of 25 lbs for less than $25 including shipping. Mineral clay stays soft and moldable as long as you keep it wet, so you don’t have to use it all at once. Many makers of figurines, cars or train miniatures use industrial design clay to create highly precised pieces but clay can also be used for bigger pieces, such as actual car bodies for the automotive industry.

Plasticine clays

Now, let’s look at more innovative clays that don’t require to rent a space in a sculpting studio. Polymer clays or plasticine clays are made of synthetic plastics and require “curing” or low heat to harden. They stay moldable for a very long time if stored properly in a plastic or metal box (no paper or fabric that would absorb the moisture). Polymer clays are usually very smooth and have a silky feeling. Some are more doughy and sticky than others. Some come in multiple colors and some don’t.

These clays are also called air and dry clays because, well, they harden in the air. They usually come in small plastic boxes of multiple colour samples.

A few brands are very well-known in the world of clay: Play Doh, Crayola and Creative Paperclay are the three stars of clay for small crafts and kids.

These 3 brands come in multiple packagings and colours. If you are trying to make a draft of a visual prototype, including for example a lot of buttons, zones and features, you may be interested by getting a bunch of different colors in one order. Each color will be used to represent a part of your product, which will make easier to visualize your idea for yourself and show it to others.

After comparing Play Doh, Crayola Model Magic and Creative Paperclay in great details, it appears that the big winner in this category is Crayola Model Magic . While a bit more expensive than Play Doh, it allows for much better quality of details. An other great advantage of Crayola Model Magic for prototyping is that it’s compatible with pens, which means that you can write and draw directly on your model. Very useful!

In the table below, I compare most plasticine clays for quick prototyping, to give you a full overview of their prices and specificities:

brand pros cons quantity price Play-Doh good smell/many colors/easy packaging not for precision/tends to brittle 2oz x 10 starts at $7.99 Creative Paperclay easy to shape/good for precision/not sticky on the hands 4oz to 16oz starts at $12.36 Crayola Model Magic can draw on it/easy to shape/multiple color/strong when cured 0.5oz single to 2lbs bucket starts at $20.39 Activa Celluclay papier mache texture/cheaper / 1 to 5 lbs starts at $10.11 Prang DAS sticky/hard to shape 2.2lbs starts at $10.49

2. Advanced sculpting

Let’s say now that you want to create a pretty advanced version of your prototype. Not just a quick visual draft but an actual form study model that will try to mimic the basic size, look and feel of the final product. Then, you will need a moldable material capable of being shaped in a very precise way, and stays exactly as you want once hardened.

That’s when it becomes interesting to look at more advanced clay materials, such as epoxy clays. Here, main brands are Sculpey, Magic Sculpt, Apoxie Sculpt, Cernit or Kato. They are usually used by sculptors and jewellery makers, who need precision and reliability. For prototyping, these types of polymer clays offer great advantages. They are clean to work with, are designed for precision work and can be used multiple times. Once hardened, they are very strong (some are close from unbreakable) and have nice soft finishing result, very similar to a smooth plastic. They usually can take many finishing techniques, such as sanding, drilling, painting, and more.

From all the brands in competition, Apoxie Sculpt is definitively number one in the prototyping category. It is as good for sculpting as its competitor Magic Sculpt but cheaper. It comes in buckets from 1 to 5 pounds and works by combining two materials: a resin and a hardener. Take a little piece of each and combine them in your hand. You will then have a few hours to shape it in the exact form you want. Apoxie Sculpt has great sculpting properties, it doesn’t stick on your hand but bond well on itself. Sharp edges and detailed parts are easy to mould. Not too soft, not too hard. The other great advantage of this brand is that it doesn’t require an oven but simply harden in the air after 4 hours. If you leave your parts outside for a night, they will become extremely hard.

In this long timelapse video, costume creator Brittany “Britthebadger” Cox shows how she created a well-finished accurate Zap Gun master using Apoxie Sculpt:

Sculpey is among the biggest brands of clay-like materials and offers many sculpting products. Their best clay for prototyping is Super Sculpey . It is easy to shape, with great bonding qualities and is pretty similar to Magic Sculpt, except that it comes ready to go. Only limit is that it needs to be cured in an oven to harden, which can’t be made in a household oven because of toxic fumes emitted by the material when baked.

If you are mostly making figurines or dolls, I would then recommend Cernit . It comes in more than 60 colors and has a finish very similar to porcelain. It is also very strong once baked. Main professionals use Cernit for making dolls and figurines that are actually used.

Once you sculpted a model, you can 3D scan it and get a 3D model that can later be edited in a modelling software. Having an actual clay model to scan makes it easier to go to the 3D modelling phase. Digital version of your model can be used for 3D printing, shared with other team members or edited in your computer for further modelling, improving and demoing.

Most 3D scanners work much better with light materials and high contrast. If you plan on making a clay model for 3D scanning, be sure to pick white or beige clays and avoid darker colors. Put your model on a high contrasted background for better render. 123D Catch by Autodesk is a free smartphone app that lets you take pictures of an object to get a 3D model that can then be edited with 123D or other tools. Useful if you haven’t yet acquired a proper 3D scanner. If you’re ready to invest, Fuel 3D gives good results for a reasonnable price.

In this comparative table, I look at all the brands of polymer clays for prototyping and show you the pros and cons, prices and quantities, from the cheapest to the most expensive ones:

brand pros cons quantity price Fimo soften easily/ not sticky small packages/not the most precise individual 25gr to packs box of 10 starts at $4.36 Cernit more than 60 colors/porcelain-like finish/great for figurines and dolls/very strong after baking difficult to condition 62g starts at $6.50 Kato very stiff/very strong when baked/21 colors (including translucent and metal) strong smell 2 oz to 12.5 oz starts at $9.00 Original Sculpey easy to shape/smooth/last for years sticky/brittle when cured 8 lbs. starts at $10.77 Sculpey Super easy to shape / good bonding / not sticky/strong when cured oven can get messy / toxic fumes 1 lb to 8 lb starts at $11.97 Sculpey Ultra Light very lightweight/very hard after baking/excellent filler extremely soft 10 oz (225 gr) starts at $14.40 Apoxie Sculpt easy to shape / good bonding / no oven needed/cheaper than competitor / 1 lb to more starts at $16.35 Sculpey III easy to push with clay guns/multicolor too soft for model making/brittle after baking 30 x 28gr starts at $16.79 Premo flexible after baking/multicolor/easy to shape/good for details 1 lb (450 gr) starts at $19.99 Magic Sculpt easy to shape / good bonding / no oven needed costly 1 lb to 5 lb starts at $28.95 Pardo no odor/made with beeswax/strong and flexible once baked/soft in its raw form/70 colors (including great translucent) more expensive than others 1.2 to 2.6 oz starts at $52.95

3. Molds and casts

Your product idea is taking shape and you are looking forward to achieve an actual functional prototype that you can test with users and show around. Creating your own mould to produce a few iteration of the prototype and see with accuracy if it fits is a necessary step. More and more inventors are now turning to 3D printing to quickly make molds out of melted plastics, but moldable plastics can be of great use at this step too. It doesn’t require you to invest in a 3D printer and allows for a more manual approach, which can be great at this step of your creative process.

Moulding materials can be flexible or solid, reusable or not. Clay can be used to make moulds, and some clays are even specifically designed for it. They work by pushing the object you want to reproduce in the clay. Once hardened, it is then the time to pour the casting material inside the mould, with any liquid or soft material (clay, chocolate, resin,…). Wait for it to harden as well. The cast has then to be removed from the mould. If properly done, the mould can be used multiple times.

Most professional mould making materials are usually silicone based. The type of silicone used is called RTV for Room Temperature Vulcanizing. It’s a stretchy and durable material combining elastomers and polymers; They have many advantages like between very strong while flexible, are good for detailed pieces and can be used multiple times. Some are also food safe, which can be good for making edible shapes. Silicone molding materials come in two shapes: pourable silicone rubber mold material and silicone mold putty.

Pourable silicone rubber mold

The pourable version works by building a box around the object and pouring the liquid silicone rubber on it. The liquid is usually a mix of two products that you have to do yourself. After about 45 minutes, the silicone starts to be cured and can de-mold after a few hours. Pourable silicone rubber can also be brushed on flat objects, like a glove.

Silicone mold putty

Silicone mold putty is much faster (and easier) to work with as it hardens after a few minutes only and creates a usuable mold in about 30 minutes. You will have to combine the two putties by hand and cover the object pretty quickly. Silicone mold putty is great for small detailed projects like connectors, jewellery or small parts for example but won’t fit your needs for bigger prototypes.

Silicone mold materials are usually expensive, about $25 per pound. Two main brands are Amazing Mold Putty and EasyMold, but you can also look up Alley Goop, Silicone Plastique (food compliant), Equinox Silicone Putty, Knead-a-Mold or Siligum. Both Amazing Mold Putty and EasyMold have the same great qualities, main difference is how stretchy and breakable the mold will be. Molds made with Amazing Mold Putty are more stretchy and breakable than those made with EasyMold.

Overall best brand for mold making is Easymold . It is easy to use and gives you a strong mold that is slightly flexible and that you can reuse multiple times. It doesn’t sweat or melt, and is great for detailed pieces as well as bigger projects. You can also use it to create textures to apply to your prototype, which can be very useful for testing a visual prototype.

brand pros cons quantity price Amazing Mold Putty stretchy mold/long lasting fast to harden/frosted resin look 300 gr (2/3 lb) starts at $22.99 Easymold Silicone Putty most acclaimed by professionals/very precise and resistant/not too bubbly/can be used for metal casting/fast dry / 1 lb starts at $29.99 Sculpey Mold Maker flexible mould not as good for details as others/not very easy to use 8 oz starts at $22.19 ComposiMold cheaper than silicon molding material/recyclable/just needs a microwave molds tend to melt/not precise enough/lots of bubbles 40 oz (1.1 kilo) $30.35

4. Connectors and additional parts

The last but not least use of clay and moldable material for prototyping is to make connectors, repair and modify existing parts. If you are for example working on an accessory for an existing product, such as a helmet mount for a GoPro camera or a smart thermos bottle handle, or anything that needs to connect to something else, some materials are exactly designed for it.

Moldable plastics

These materials are called moldable plastics. They are part of the air and dry category and usually don’t need to get cured in an oven. Most of them work by pouring pellets of plastics into a bowl of hot water (70°C/160°F). You will then have to toss and combine pellets and shape the material in the desired form. Moldable plastic hardens fast so you will have to dip it quickly in hot water to keep being able to shape it. Result is a very strong object than could be used every day and gives you a glossy professional finish.

For more precise parts, you can also use moldable plastics as casting or molding material by applying it on an existing mould or object. Main brands of moldable plastics are Shapelock and InstaMorph. Shapelock is the historical brand but InstaMorph is currently the most distributed and the most popular brand. It comes in 12 ounces jar that cost a bit more than $15, and can be reused multiple times.

Connecting paste

I also put the famous Sugru in this category because it is specifically designed for repairing and connecting things, even though it works more like a polymer clay. Sugru comes in small one-use packages, as a very sticky paste. It cures in the air and becomes a very strong waterproof slightly flexible material. Sugru can be of great help for prototyping if you need to connect two parts, create a joint or solidify a fragile piece.

Check the table below for a full comparison.

brand pros cons quantity price Sugru excellent bonding / smooth / easy to shape / multicolor / waterproof / UV resistant sticky / costly / 6 months expiration date / small quantities individual mini pack to 8 packs to more 8-packs starts at $8.40 InstaMorph most popular product/big user community/easy to use sticky if overheated 12 oz starts at $16.99 Shapelock reusable/tough/non-toxic/great for molds and mechanical parts/paintable no storing box 250gr starts at $14.95 Polymorph cheapest product/comes in bigger quantities no storing box 8 oz to 35 oz (50 gr to 1000 gr) starts at $11.95 Thermomorph good price/easy to use gets sticky if overheated 17.8 oz starts at $19.97

And the winners are…

Overall best choice for prototyping: Apoxie Sculpt

Best choice in the quick sculpting category: Crayola Model Magic (2nd: Creative Paperclay )

Best choice in the advanced sculpting category: Apoxie Sculpt (2nd: Super Sculpey )

Best choice in the mold maker category: Easymold

Best choice in the moldable plastic category: InstaMorph

Extra tip: think of wearing plastic gloves if you are working a lot with clay.

Hope you’ll enjoy this article, let me know in the comment how your prototyping is going.

Credit featured image: Simon Collison

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