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Gelatine bioplastic

Teacher pack, A New Field biomaterials lab

Level: UK, KS3 Science

Group: 24 students

Session: 60 min

Difficulty: Beginner

1. Teacher intro script

Today we are going to make a new material from scratch. Not shape it, not decorate it, not assemble it from parts, but actually make it. We are going to start with gelatine, water and a little glycerine, and by the time we finish you will be holding a flexible, translucent sheet that behaves a lot like a plastic film but comes apart in a compost bin in a matter of weeks. Gelatine is a protein. It comes from collagen, the same long-chain molecule that builds up in our skin and in the tendons and bones of animals. When we heat it in water the collagen uncoils into long strings. When those strings cool and dry, they tangle back together and lock each other in place. That tangle is the sheet you are going to see emerge on the tray. The glycerine we add is there to slip between the strings so they can bend past each other, which is what turns a brittle dried film into something flexible. That small trick, adding a go-between to stop a material snapping, is one of the oldest moves in materials science, and it underpins a huge part of the plastics industry. As we work, pay close attention to three moments. The first is the moment the gelatine swells in cold water before we heat it. The second is when the hot mixture becomes clear, smooth and pourable. The third is when you peel the dry sheet off the tray tomorrow. In each of those moments the same ingredients are doing very different things. If you can describe what is happening at each stage, you are already thinking like a materials scientist.

1b. Core practical mapping

Modelled on the Edexcel GCSE (9-1) Core Practical Guide so the session slots into an existing scheme of work.

Practical: Investigate the effect of glycerine content on the flexibility and clarity of cast gelatine bioplastic films

This practical asks students to make a cast gelatine bioplastic from a known recipe, then to vary one ingredient (the glycerine plasticiser) across two or three batches and compare the finished sheets. The session sits naturally inside topics on polymers, materials and their properties, sustainable design, and working scientifically. It is hands-on, low-cost, runs in a single double lesson with a 24 to 48 hour drying window, and produces a take-home sample for every student.

Links to the specification content

WS Working scientifically: planning a fair test, identifying independent, dependent and control variables, taking accurate measurements, evaluating results.
POL Polymers: long-chain molecules, the role of plasticisers in modifying flexibility, and the difference between thermosetting and thermoplastic behaviour.
PROT Biological molecules: proteins as long chains of amino acids; gelatine as denatured collagen.
MAT Properties of materials: comparing materials by observable and measurable properties such as flexibility, clarity, density and water resistance.
ENV Sustainability: life-cycle thinking, biodegradability and the environmental case for bio-based alternatives to conventional plastics.

Questions to ask, to enhance learning

What is the independent variable in this practical, and what are you keeping constant to make the comparison fair?
How will you measure the difference in flexibility between two finished sheets in a way that another group could repeat?
What does the glycerine actually do at the molecular level, and how would you explain that to someone who has not studied polymers?
Why does the mixture become clear when it heats, and what is happening to the collagen chains at that moment?
If you doubled the amount of glycerine, what would you predict happens, and is your prediction supported by the result?
What sources of error in this method might make two groups using the same recipe get different sheets?
Which industrial polymer process is the closest analogue to what you have just done, and where do the analogies break down?
If you wanted to make this material genuinely waterproof, what is the next variable you would test, and why?
What everyday plastic product could this material plausibly replace, and what tests would have to be passed before a brand could switch to it?

Skills covered in the practical

Accurate measurement of mass to one decimal place using a digital balance
Accurate measurement of volume in millilitres using a measuring cylinder
Safe handling of a hot solution and supervised work at a heat source
Casting a thin film of consistent thickness across a flat tray
Recording observations at clearly defined points in the method (dry, bloomed, dissolved, cast, dried)
Producing a labelled sample card and comparing finished samples by stated properties

Maths skills

Measurement to one decimal place in grams and millilitres
Working with ratios between ingredients (gelatine to glycerine to water)
Calculating percentage change in glycerine between two batches
Plotting flexibility scores or thickness against glycerine content on a simple bar chart
Estimating the area of a cast sheet in square centimetres

Sample question

A student made two batches of gelatine bioplastic using the same method but changed only the amount of glycerine. Batch A used 6 g of glycerine. Batch B used 12 g of glycerine. After drying, the student described Batch A as stiff and brittle and Batch B as soft and easy to bend. Explain, in terms of the polymer chains in the dried film, why the two batches behaved differently, and describe one further test the student could carry out to compare the two materials more rigorously. (6 marks)

Mark scheme. Award up to three marks for a correct mechanistic explanation: glycerine acts as a plasticiser; small glycerine molecules sit between the long protein (collagen) chains in the dried film; this stops the chains locking rigidly together; chains can slide past one another, which lets the film bend rather than crack. Batch B has roughly twice as much glycerine, so more space between chains, so the film is softer and more flexible. Award up to three further marks for a sensible further test described clearly: a quantitative measurement of flexibility (such as the bend angle before fracture, the mass needed to deform a strip a fixed amount, or repeat fold tests to failure); a stated control (sheets cut to the same size and thickness, tested in the same conditions); and a way of recording the result that another group could repeat (mean of three trials, with a brief written evaluation).This question rewards students who can connect a macroscopic property (flexibility) to a molecular-level explanation (plasticiser action between polymer chains), and who can design a fair quantitative comparison rather than relying on subjective description.

2. Discussion guide

Opening

Hold up a plastic carrier bag. Ask, how long do you think this has existed as a material? Let a few students guess. The answer is about seventy years, which in the long history of things people have made is almost nothing. Today we are going to make a material that could, in some uses, do the same job as that bag. The difference is that ours will come from the kitchen cupboard and will break down in the ground.

During the class

As the class works, move between groups and keep conversation flowing. Your role is less demonstrator and more scientific companion. Students will naturally want to describe what they see, so push them for precise language from the very first step. Is the dry gelatine granular or powdery? Does it smell of anything? When it blooms in cold water, how has it changed? They will want to say it looks like jelly. That is true but lazy. Press them. Is it swollen, translucent, gel-like, rubbery. Those words earn their keep because they map directly onto the scientific concept of a hydrogel, which is exactly what bloomed gelatine is. Once the mixture hits the heat the conversation should shift to cause and effect. Why does the mixture go clear? The answer is that the collagen chains are uncoiling and spreading out through the water. What would happen if we boiled it hard? Most students will guess, correctly, that it might damage the protein. What if we used more glycerine? Ask them to predict before you tell them. A group that predicts out loud and then tests in the pour has just run a variable test, which is the core move of scientific method. During the pour, focus on craft. The thickness of the pour sets the final feel. A thin pour dries faster and gives a crisper sheet. A thicker pour gives a floppier, more rubbery one. Ask each group to make an intentional choice and write down what they chose and why. This is also the moment to introduce fillers. If a group has sieved in some coffee grounds or fine sawdust, ask them what the filler is doing. It is adding body, yes, but it is also scattering light, adding grip, giving the sheet a texture that pure gelatine does not have. That shift from film to composite is worth naming. In the drying phase, with the sheets cooling on trays, turn the discussion to function and use. Pass round a range of common objects, a cling film wrapper, a window, a cellophane sweet bag, a leaf. Ask, which of these could our material replace? Which could it absolutely not? A sheet of gelatine bioplastic is lovely for a window film or a decorative insert, it is not likely to hold a sandwich together in a packed lunch. That honest conversation about what a material can and cannot do is the discussion students will carry with them long after the session ends. Close the discussion by bringing it back to the animals behind the gelatine. This is an animal-derived material. Tomorrow we could run the same session with agar agar, a seaweed, and get a vegan film with a very different character. Ask the group to imagine a version of this recipe using a material sourced locally to where they live. What would change?

Closing

Ask every group to describe their sheet in exactly three words and write those words on the board. Look at the range as a class. What patterns do you see, and what does that tell you about how much variation one simple recipe can produce?

Prompts to pull from

What does this sheet remind you of, and why?
If you were selling this material to a packaging designer, what would you say?
Which ingredient is doing the most important job in this recipe, and how do you know?
Why do you think glycerine makes the sheet flexible rather than brittle?
What would you change about this recipe if you wanted a stiffer sheet, and why?
Where in nature do you already find long protein chains doing a structural job?
What is one product this material could realistically replace, and one it could not?
If gelatine comes from animals, what are the ethical questions we should ask about using it at scale?

3. Minute-by-minute run sheet

Time	Activity
0 – 6 min	Introduction. Read the intro script, set expectations and show a finished sample if you have one.
6 – 11 min	Bloom the gelatine in cold water. Weigh 15g of powdered gelatine into a small bowl. Pour in 75ml of cold water and leave it for about five minutes without stirring. The gelatine will swell into a soft, wobbly jelly. This step rehydrates the collagen before heat gets near it, which gives a smoother final film. Teacher tip: This is the quietest step of the lesson and a good moment for the opening discussion. Ask students to describe the gelatine before and after blooming. Precise observation language here sets the tone for the rest of the session.
11 – 21 min	Warm and combine the mixture. Transfer the bloomed gelatine to a saucepan over a low heat. Add 6g of glycerine. Stir gently with a wooden spoon as the mixture warms. It should turn clear and pour freely off the spoon after two to three minutes. Do not let it boil. Teacher tip: The moment the mixture turns from cloudy to clear is the moment the collagen chains fully uncoil. Name it out loud when it happens. Students who spot it find the chemistry easier to hold on to later.
21 – 26 min	Add any filler or pigment. If a group is using a filler or pigment, sieve or strain it into the pan now and stir until evenly distributed. Keep the heat low. Aim for a pourable mixture with no lumps visible as you lift the spoon. Teacher tip: Each group can make this their variable: no filler, coffee grounds, charcoal, onion skin infusion, turmeric. Ask them to predict the finished sheet before they pour.
26 – 36 min	Pour and cast on the tray. Line a flat tray with baking paper or a silicone mat. Pour the mixture across the tray and tilt gently so it spreads into an even layer. Aim for a layer about the thickness of a pound coin. Tap the tray lightly to release any bubbles. Teacher tip: The pour is where craft shows up. A fast, confident pour gives a cleaner edge. A hesitant pour trails strings. Demonstrate once before letting groups do their own.
36 – 50 min	Dry, peel and trim the sheet. Leave the cast sheet to dry flat, out of direct sun, for 24 to 48 hours until it peels away cleanly from the baking paper. Trim the edges with scissors. Label each sheet with the group's name, filler choice and date. Teacher tip: Drying is slow and usually falls outside the teaching window. Cast at the end of one session and peel at the start of the next. The peel itself is a small ritual that works well as a lesson opener.
50 – 54 min	Compare, evaluate and archive. Lay every finished sheet on a labelled tray. Each group describes three properties of their sheet and names one change they would make next time. Photograph the full tray against a plain background for the class archive. Teacher tip: A side by side tray is the single best visual of the session. It turns an individual result into a class-level pattern and makes the reflection discussion much easier to run.
54 – 60 min	Wrap-up. Run the closing discussion, label samples, photograph for the class archive and pack down.

4. Ingredients and equipment

Fixed ingredients

Gelatine, 15g. Bloom in cold water 5 min first.
Glycerine, 6g. More for floppier film.
Water, 75ml. Warm, not boiling.

Flexible inputs

Filler (optional), up to 10g. Try: Coffee, tea leaves, fine sawdust, bark (ground)
Pigment (optional), to taste. Try: Turmeric, onion-skin infusion, charcoal

Equipment

Saucepan, wooden spoon, thermometer (optional), baking paper, flat surface or tray.

4a. The foraged ingredient (optional, highly recommended)

Spent coffee grounds. Spent coffee grounds is one of several cellulose-rich powders that work for this recipe; see 'Use what you have' above. Sieved fine, coffee grounds act as a cellulose-rich filler and natural pigment. They give the finished film body, a warm brown tone, and a subtle grainy texture that plain gelatine cannot produce on its own.

A sheet made with foraged coffee grounds tells a story. Students can see where the material came from, and the class ends with a sample that carries the smell and colour of a real local source. It turns the session from a chemistry demonstration into a proper material investigation, where the ingredient is something the class chose and collected themselves.

Without it: The recipe still works beautifully with only gelatine, glycerine and water. The film will be clear, warm-amber and fully usable. You lose the story and the texture, but you keep the core science.

Route A, Teacher prepares in advance (+20 min)	Route B, Students source as part of the lesson (+30 min)
Collect coffee grounds ahead of the session, dry them, sieve them, and have them ready in a labelled jar so the class can scoop straight into the mix. A week ahead, ask the staff room or a local cafe to set aside their spent espresso pucks and filter grounds. Two or three teaspoons per group of four students is plenty. Spread the damp grounds in a thin layer on a baking tray lined with parchment. Dry in a low oven (around 80 degrees Celsius) for 30 to 40 minutes, or leave on a warm radiator overnight. The grounds should be dusty-dry and crumble easily between finger and thumb. Sieve the dry grounds through a fine tea strainer to remove any coarse pieces. A finer grind gives a smoother film. Store in a sealed jar at room temperature. They will keep for months. Label with the date and the source cafe so students know the provenance.	Students visit the staff room or a friendly local cafe to ask for spent grounds, carry them back, dry them and sieve them as a preparation activity before the main recipe begins. Before the making session, frame the foraging as a small material expedition. Agree as a class which sources to ask (staff room, nearest cafe, a parent's kitchen). Teach the script: who we are, what we are doing, what we are asking for. Send groups of two or three, with an adult for younger classes. Take a lidded tub to carry the damp grounds home. Thank the source and ask whether they would like to see the finished sample. Back in the classroom, spread the grounds on a lined tray. If there is access to an oven, dry at low heat for 30 minutes. If not, drying on radiators or sunny windowsills for a day or two works well, with a second session to finish the recipe. Once dry, let students crumble and sieve the grounds through a tea strainer. Discuss what they see, smell and feel. Dry grounds smell different from wet, and sieving separates coarse from fine, both are useful observations. Weigh out the sieved grounds into labelled cups, ready to fold into the gelatine mix. Each group can sign the cup with their name and the source, so the finished samples are tagged with their own provenance.

Route A, Teacher prepares in advance (+20 min)

Route B, Students source as part of the lesson (+30 min)

Collect coffee grounds ahead of the session, dry them, sieve them, and have them ready in a labelled jar so the class can scoop straight into the mix.

A week ahead, ask the staff room or a local cafe to set aside their spent espresso pucks and filter grounds. Two or three teaspoons per group of four students is plenty.
Spread the damp grounds in a thin layer on a baking tray lined with parchment.
Dry in a low oven (around 80 degrees Celsius) for 30 to 40 minutes, or leave on a warm radiator overnight. The grounds should be dusty-dry and crumble easily between finger and thumb.
Sieve the dry grounds through a fine tea strainer to remove any coarse pieces. A finer grind gives a smoother film.
Store in a sealed jar at room temperature. They will keep for months. Label with the date and the source cafe so students know the provenance.

Students visit the staff room or a friendly local cafe to ask for spent grounds, carry them back, dry them and sieve them as a preparation activity before the main recipe begins.

Before the making session, frame the foraging as a small material expedition. Agree as a class which sources to ask (staff room, nearest cafe, a parent's kitchen). Teach the script: who we are, what we are doing, what we are asking for.
Send groups of two or three, with an adult for younger classes. Take a lidded tub to carry the damp grounds home. Thank the source and ask whether they would like to see the finished sample.
Back in the classroom, spread the grounds on a lined tray. If there is access to an oven, dry at low heat for 30 minutes. If not, drying on radiators or sunny windowsills for a day or two works well, with a second session to finish the recipe.
Once dry, let students crumble and sieve the grounds through a tea strainer. Discuss what they see, smell and feel. Dry grounds smell different from wet, and sieving separates coarse from fine, both are useful observations.
Weigh out the sieved grounds into labelled cups, ready to fold into the gelatine mix. Each group can sign the cup with their name and the source, so the finished samples are tagged with their own provenance.

Shopping list for 24 students (6 batches)

Ingredient	Role	Need	Buy	Est. cost
Gelatine (powder or leaf)	Film-former	90g	1 × 250g	£7.49
Vegetable glycerine	Plasticiser	36g	1 × 500ml	£7.99
Tap water	Solvent	450ml	,	,
Coffee	Filler (optional)	60g	,	,
Turmeric	Pigment (optional)	Recipe calls for: to taste	1 pack	,
Estimated Amazon total				£15.48

Foraged and tap-water items are excluded from the cost. For schools with a preferred supplier, use the pack sizes above as a guide.

5. Curriculum mapping

KS3-MC, Materials and chemical reactions

Step	Links to	Evidence
Preparing and massing ingredients to a brief	Science: working scientifically, designing a fair test, controlling variables. D&T: working with a materials brief	Worksheet shows the chosen variable for the group and the constants held fixed.
Heating and understanding dissolution	Science: Chemistry, solutions, the behaviour of particles in a dissolving solid	Diagram of particle behaviour as the gelatine dissolves, labelled.
Introducing the plasticiser	Science: Chemistry, polymers, the role of additives in modifying material properties	Short written explanation of how glycerine changes the final sheet, using the words polymer and plasticiser correctly.
Casting and drying	D&T: understanding properties of materials and informed material selection	Sample card labelled with the recipe choice, predicted behaviour and actual behaviour.
Evaluating the finished material	Science: working scientifically, evaluating results, identifying further questions. D&T: iterative design	Evaluation paragraph with at least one suggested improvement and a reason.

6. Risk assessment

Hazard	Who	Severity	Controls
Hot liquid at the stove	Student at the hob, anyone passing the cooking area	Medium	Adult supervises the stove at all times. Heat gelatine mixture gently, do not boil hard. Use a rear ring if the hob has one. Only the adult, or a nominated older student under direct supervision, pours hot mixture onto the tray. Keep the pouring surface clear and stable.
Steam and minor burns during pour	Student pouring or holding the tray	Low	Oven gloves or a folded tea towel when handling the pan. Pour away from the body. Let the mixture cool for one minute off the heat before pouring for thicker casts.
Animal-derived ingredient (gelatine)	Students following a vegetarian or vegan diet, or with cultural restrictions on pork or beef gelatine	Low	Check dietary and cultural preferences before the session. Offer the agar recipe (R002) as a like-for-like alternative. Name the source of the gelatine clearly at the start of the session so students are informed.
Glycerine on skin	Students handling the plasticiser	Low	Glycerine is non-toxic and widely used in cosmetics. Ask students to wash hands after handling and to avoid rubbing their eyes until they have done so.
Slips and spills	Whole class	Low	Cover work surfaces with baking paper or oilcloth. Keep a cloth to hand. Wipe any spills immediately. Bin soaked paper towels at the end of the session.
Sharp tools at finishing	Students trimming dry sheets with scissors or scalpels	Low	Age-appropriate tools only. Demonstrate the cut before students begin. Use a cutting mat. Keep fingers behind the blade at all times.

Teacher signature

Date

7. Product ideas

Stained-glass window insert

Use pigmented gelatine films to build a small panel that sits in front of a window, layering translucent sheets between two thin battens. The material takes light beautifully and softens colour rather than blocking it.

Skills: Colour mixing in a liquid mix, Sheet-to-sheet registration, Simple framing. Extension: Add a pressed leaf or petal between two layers while still tacky, and compare how the inclusion ages over a term.

Seed packet window

Design a paper seed packet with a gelatine bioplastic window that shows the seeds inside. The window itself is compostable, so the packet can be buried whole at the end of its life.

Skills: Packaging design, Cutting and scoring card, Joining paper to film. Extension: Run a usability test: can a gardener read the sowing instructions through the window after the packet has been left on a shed shelf for a week?

Book jacket or bookmark

Cast a thin sheet and cut into bookmarks or a protective jacket for a hardback. Pigment it with onion-skin infusion or charcoal for a range of warm, graphic tones.

Skills: Trimming to consistent width, Surface finish, Working with a deckle edge. Extension: Compare how the bookmark feels in the hand after one week of use against a paper bookmark of the same size.

Jewellery blanks

Cast a thicker sheet, let it dry for an extra day, then cut into geometric blanks for earrings or pendants. Drill a single hole for the fitting once the sheet is fully cured.

Skills: Drawing to scale, Punch or drilling, Finishing edges with a fine sandpaper. Extension: Set up a short market stall at a school event and record what customers notice first about the pieces.

Stage prop window panels

Cast large, very thin sheets and use them as period window panes for a school play. They catch light and look handmade in a way that modern plastics do not.

Skills: Working at scale, Mounting to a wooden frame, Backstage handling. Extension: Document the sheets through the run of the show and note how they behave under stage lights.

Temporary event signage

Make pigmented sheets that act as eye-catching signs for a one-day event, then compost them afterwards. Keep the text simple and bold so it reads across the room.

Skills: Typography at scale, Pigment loading, Mounting on a sandwich board. Extension: Weigh each sign before use and again after composting, to measure how much has broken down in a fortnight.

8. Teacher crib sheet

The science

Gelatine is collagen that has been partially broken down by heat. Collagen itself is the most abundant protein in the animal kingdom, making up the fibrous scaffolding of skin, tendons, ligaments and bones. Each collagen molecule is a long triple helix of three protein chains. When you heat gelatine in water above about 40 degrees Celsius, the helices unwind into loose strings. When the solution cools and dries, those strings reform a tangled network, trapping water as they go. That network is what we see and feel as a cast film. Adding a plasticiser like glycerine is the quiet hero of the recipe: small glycerine molecules sit between the long protein strings and stop them locking rigidly into place, which lets the dried sheet flex rather than shatter. In industrial terms this is the same principle used to plasticise PVC in cling film or shower curtains, just with a plant-derived, non-toxic small molecule instead of phthalates.

Natural history

Collagen evolved around six hundred million years ago, and its appearance in the fossil record is closely tied to the first animals with complex body plans. Almost every multicellular animal alive today relies on collagen for structure, from the flexible cartilage of a shark to the ligaments holding your elbow together. Because it is so widespread, collagen has been in the human material repertoire for as long as we have butchered animals. Archaeological sites show evidence of hide glue, which is functionally a close cousin of gelatine, going back more than eight thousand years, used to haft tools, repair pots and bind the layers of early composite bows. In other words, casting a gelatine film in a classroom in 2026 sits in a material tradition that spans almost the whole of human civilisation.

Creative context

Gelatine-based materials are experiencing a quiet revival in contemporary design. Studio Swine's early work explored gelatine and hair to make fashion accessories. Shahar Livne has worked at the intersection of bio-based plastics and speculative design. At a smaller scale, the Materiom platform, FabTextiles at Fab Lab Barcelona and Elvira Sopos's kitchen experiments have shared open recipes for gelatine films, each tweaking the formulation to hit a particular texture or behaviour. Gelatine is also quietly everywhere in the photographic tradition: the silver halide layers in traditional photographic film and paper are suspended in gelatine. Every black and white negative you have ever seen owes its image to a gelatine emulsion, which means students making a film in a classroom today are working in the same material family as nineteenth century photographers.

Key terms

Term	What it means
Protein	A large biological molecule built from a chain of amino acids, folded into a specific shape. Gelatine is a protein.
Collagen	The specific protein, built as a triple helix, that gives structure to skin, bone and connective tissue in animals.
Denaturation	The process by which heat, acid or other stressors cause a protein to unwind from its folded shape. Gelatine is denatured collagen.
Plasticiser	A small molecule added to a polymer to reduce brittleness. Glycerine is doing this job in the recipe.
Cast film	A thin, flat sheet of material made by pouring a liquid onto a flat surface and letting it dry there.
Biodegradable	A material that can be broken down by living organisms into harmless substances within a reasonable timeframe.