You’ve got a stack of plastic water bottles on the counter and a curious kid asking to make Shrinky Dinks. Before you preheat that oven, there’s one thing every crafter should know: not all plastic shrinks the same way, and the number stamped on the bottom of that bottle matters more than you might think.
What Is Number 1 Plastic?
Number 1 plastic carries the resin identification code #1, which stands for Polyethylene Terephthalate — commonly known as PET or PETE. It’s the most widespread plastic in everyday consumer life. Think water bottles, soft drink bottles, salad dressing containers, and peanut butter jars. That little triangle symbol with a “1” inside is everywhere, which is exactly why so many crafters wonder if they can repurpose it.
PET is lightweight, semi-rigid, and highly impact-resistant. Its melting point sits at roughly 250°C (482°F), but it begins to soften and deform at temperatures as low as 60°C (140°F). That temperature sensitivity matters a great deal when you plan to run it through a home oven.
How Shrinky Dinks Actually Work
Before judging what #1 plastic can or can’t do, it helps to understand the science behind the shrink.
Shrinky Dinks rely on a process called polymer memory. When plastic is manufactured, it gets stretched and rapidly cooled, locking its molecules in a thin, flat orientation. Heat reverses that process — the polymer chains “remember” their original compact form, bunch back together, and the plastic shrinks while thickening.
The key word here is specific. This memory-release only happens reliably when the plastic polymer is the right type and processed in a way that stores enough molecular tension to be released. Not every plastic is manufactured with that kind of oriented stretching.
The Short Answer: Does Number 1 Plastic Work?
Technically, yes — but barely, and not well.
Number 1 plastic shrinks a little when heated, but it mostly turns white, curls unevenly, and produces unpredictable results. Crafters who’ve tried it report that the finished piece looks cloudy, warped, and nothing like the crisp, thick charms you get from commercial Shrinky Dink sheets.
One tester who tried a Minecraft figure cutout from #1 plastic said flatly: “It shrinks a little, but mainly turns white.” That’s a far cry from the satisfying curl-and-flatten magic you want from a proper shrink project.
| Plastic Type | Shrinks Well? | Result Quality | Safety at Oven Temp |
|---|---|---|---|
| #1 PET | Partially | Turns white, curls unevenly | Generally low toxicity |
| #5 PP | Poorly | Inconsistent, often warped | Not recommended for crafting |
| #6 PS (Polystyrene) | Yes — best option | Clear, crisp, thick charms | Use ventilation; styrene concern above 170°C |
| Commercial Shrinky Dink sheets | Yes — ideal | Perfect, uniform, consistent | Safe as directed |
Why #1 Plastic Underperforms
The Molecular Structure Problem
PET’s polymer chains are not oriented in the same way as polystyrene (#6). When manufacturers produce PET bottles, the stretching process locks molecules differently than the biaxially-oriented polystyrene used in shrink plastic. The result? When you heat #1 plastic, there simply isn’t enough “stored memory” in the right form to produce a clean, uniform shrink.
The Temperature Mismatch
PET requires a higher softening temperature than polystyrene to begin deforming. At standard Shrinky Dink oven temperatures of around 325–350°F, PET doesn’t reach the point where it shrinks cleanly — it deforms, whitens, and buckles instead. You’d need higher heat to coax any real shrinkage, but that risks burning, smoking, or warping the piece into an unusable lump.
The Whitening Effect
The cloudy white transformation that #1 plastic undergoes when heated is a sign of crystallization — a structural shift in the PET polymer. Crystallized PET (known as CPET) is actually more heat-resistant, not less. This is the opposite of what you want for a Shrinky Dink. Instead of shrinking down and thickening into a vibrant charm, the plastic stiffens and becomes opaque.
What Plastic Actually Works for DIY Shrinky Dinks?
#6 Polystyrene — The Gold Standard
The clear winner for DIY shrink crafts is #6 plastic (Polystyrene or PS). It’s the same polymer used in commercial Shrinky Dink products. You can identify it by the recycling triangle with a “6” stamped on the bottom of clear, rigid containers — think deli clamshells, clear bakery boxes, and certain takeout containers.
When heated at 325–350°F, #6 plastic curls dramatically, then flattens back out, shrinking to roughly one-third its original size while becoming noticeably thicker and more rigid. The result is exactly what every shrink crafter wants.
A Step-by-Step Guide to DIY Shrinky Dinks with #6 Plastic
| Step | Action | Details |
|---|---|---|
| 1 | Find your plastic | Look for clear containers marked #6 on the bottom |
| 2 | Clean thoroughly | Wash with dish soap and dry completely |
| 3 | Cut your shapes | Use sharp scissors; cut slightly larger than your desired final size |
| 4 | Decorate | Use permanent markers (Sharpies) or felt-tipped pens |
| 5 | Punch holes | Use a hole punch before baking if making charms |
| 6 | Line your tray | Use parchment paper on a baking sheet |
| 7 | Preheat the oven | Set to 325–350°F |
| 8 | Bake and watch | Pieces curl then flatten — remove when flat, about 1–3 minutes |
| 9 | Press flat if needed | Use a spatula or flat object immediately after removal |
| 10 | Ventilate the room | Keep windows open; work in a well-aired space |
Safety: What You Need to Know Before Baking Any Plastic
Number 1 PET — Relatively Safe When Heated
Under normal oven temperatures, PET does not release toxic fumes. PET only begins to break down chemically at extreme heat far beyond what a craft session requires. That said, it still doesn’t produce useful shrinking results, so safety isn’t really the reason to avoid it — ineffectiveness is.
Number 6 Polystyrene — Ventilation Is Essential
Polystyrene is more effective for shrinking but raises more legitimate safety questions. It can release styrene vapor when heated, particularly if temperatures exceed 170°C (338°F). Prolonged or repeated exposure at high concentrations carries health risks, including respiratory irritation.
Practical safety rules for #6 shrink crafts:
- Keep oven temperature at or below 325°F
- Never exceed 3 minutes of baking time
- Always work in a ventilated space — open windows, run a fan
- Supervise children at all times
- Consider using a dedicated toaster oven kept away from living areas
Plastics to Never Bake for Crafts
Some plastics are flatly dangerous when heated. #3 PVC releases chlorine compounds. #7 plastics are a mixed bag of unknown polymers. Stick to #6 for DIY shrinking, or simply buy commercial shrink plastic sheets for the safest, most consistent results.
When Might #1 Plastic Be Worth Trying?
There’s one narrow scenario where experimenting with #1 plastic makes sense: CPET (Crystallized PET), a processed variant of #1 plastic that’s deliberately heat-stabilized for oven-ready food trays. CPET is always opaque (never clear), and it can withstand temperatures up to 400°F without deforming. However, it won’t shrink in a useful craft sense — it’s designed to resist deformation, not embrace it.
For casual craft experimentation, testing a small scrap of #1 plastic costs nothing. But set realistic expectations: you’ll likely get a whitened, curled, unusable piece rather than a charming shrunken trinket.
The Best Alternatives to DIY Shrinky Dinks
If #6 plastic is hard to find or you want guaranteed results, these options deliver:
- Commercial Shrinky Dink sheets — widely available at craft stores like Michaels or JoAnn; shrink uniformly and predictably every time
- Grafix Shrink Film — a popular brand offering both clear and frosted finishes with reliable shrink behavior
- Printable shrink plastic — accepts inkjet or laser printing for photographic detail before baking
Key Takeaways
- Number 1 plastic (PET) does not work well for Shrinky Dinks — it partially shrinks but mostly turns white, curls unevenly, and produces poor results
- #6 polystyrene is the correct plastic for DIY Shrinky Dinks; it shrinks cleanly, thickens nicely, and mimics commercial shrink sheets
- The failure of #1 plastic comes down to molecular structure and temperature mismatch — PET’s polymer chains don’t carry the same stored orientation as polystyrene
- Safety matters with any baked plastic — always ventilate when using #6, and keep temperatures below 325–350°F
- When in doubt, buy commercial shrink plastic sheets for consistent, child-safe, beautiful results every single time
Frequently Asked Questions (FAQ)
Can you use #1 plastic bottles for Shrinky Dinks?
Technically you can try, but #1 PET plastic doesn’t shrink properly — it mostly turns white and curls rather than producing a clean, flat, thickened charm. The molecular structure of PET simply isn’t designed to store and release the kind of polymer memory that polystyrene does. Save the water bottles for recycling and source #6 plastic instead.
What happens when you put number 1 plastic in the oven?
At Shrinky Dink temperatures (325–350°F), PET begins to soften and crystallize, turning the plastic opaque and causing irregular curling. It doesn’t shrink uniformly or thicken the way #6 polystyrene does. In some cases, it may also warp beyond recognition or simply melt unevenly.
Why does number 6 plastic work for Shrinky Dinks but number 1 doesn’t?
Polystyrene (#6) is manufactured through a process that biaxially stretches and rapidly cools the plastic, locking polymer chains under tension. Reheating releases that tension, causing the reliable curl-then-flatten shrink. PET (#1) doesn’t carry the same orientation or tension in its polymer chains after manufacturing, so heating it produces crystallization rather than shrinkage.
How do you find #6 plastic for homemade Shrinky Dinks?
Look at the bottom of clear, rigid food containers — deli clamshells, clear bakery boxes, and some clear takeout containers often carry the #6 recycling symbol. Avoid foam or Styrofoam products even though they’re also #6; you want the clear, flat, rigid variety.
Is it safe to bake #1 plastic in a home oven?
PET plastic is generally low-toxicity at normal temperatures and doesn’t emit harmful fumes under typical baking conditions. However, the real concern with baking any plastic at home is ventilation — always open windows and keep children supervised. Since #1 plastic doesn’t produce usable Shrinky Dink results anyway, there’s little reason to bake it.
What temperature do you use for DIY Shrinky Dinks with #6 plastic?
The ideal oven temperature is 325–350°F (163–177°C). Going higher increases the risk of styrene release from the polystyrene and can cause the plastic to melt or burn rather than shrink cleanly. Most pieces are done within 1–3 minutes — watch them the whole time and remove them once they flatten back out after curling.
Can you color number 1 plastic before trying to shrink it?
Yes, permanent markers (like Sharpies) adhere to PET surfaces. The coloring isn’t the problem — the shrinking is. Even beautifully colored #1 plastic will lose its crispness and turn whitish-opaque during baking, obscuring your design. If you want vivid, lasting color on a shrunken charm, use #6 plastic or commercial shrink plastic sheets as your base.
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