How to Identify the Type of Plastic in Your Everyday Items

Knowing what plastic your object is made from helps you recycle correctly and avoid harmful chemicals. Below are three reliable, industry‑approved methods to determine a plastic’s identity.

1. Resin Identification Code (RIC)

The Resin Identification Code, introduced by the Society of the Plastics Industry (SPI) in 1988, is the most common visual cue. Codes 1–7 represent the seven major thermoplastic families:

#1 PET / PETE – Polyethylene terephthalate (e.g., soda bottles)
#2 HDPE – High‑density polyethylene (e.g., milk jugs, trash bags)
#3 PVC – Polyvinyl chloride (e.g., pipes, vinyl siding)
#4 LDPE – Low‑density polyethylene (e.g., plastic bags, food wraps)
#5 PP – Polypropylene (e.g., yogurt containers, bottle caps)
#6 PS – Polystyrene (e.g., Styrofoam cups, disposable plates)
#7 Miscellaneous – Includes polycarbonate, nylon, ABS, acrylic, PLA, etc.

Example: A labeled container with a “5” is polypropylene, while a typical Styrofoam cup bears a “6” at its base.

How to Identify the Type of Plastic in Your Everyday Items

2. Burn Test (Use Caution)

Burn testing reveals a plastic’s combustion profile, but it should only be performed in a well‑ventilated, industrial setting due to toxic fumes. When a sample is heated with a lighter, observe the odor, flame color, dripping, and floating behavior. Refer to the table below for key indicators.

Material	Odor	Flame Color	Drips?	Float?
ABS	Acrid, black smoke with soot	Orange	No	No
PETE / PET	Light smoke	Yellow	Yes	Yes
PTFE	Burnt‑hair scent	—	No	No
Nylon	Burnt wool or hair	Blue, yellow tip	Yes	No
Polycarbonate	Faint sweet aroma, black smoke with soot	Orange	Yes	No
Polyethylene	Candle wax	Blue, yellow tip	Yes	Yes
Polypropylene	Sweet odor	Blue, yellow tip	No	Yes
Polystyrene	Gas odor (naphtha)	Yellow, black smoke	Yes	No
PVC	Hydrochloric acid	Yellow with green spurts	No	No
Polyesters	Hydrochloric acid	Yellow	No	No

3. Float or Sink Test

Density dictates whether a plastic will float. Plastics with a density lower than water (1.00 g/mL) will float; those above will sink. The following density ranges are typical:

Float: HDPE (0.95–0.96), LDPE (0.92–0.94), PP (0.90–0.91)
Sink: PETE (1.38–1.39), PVC (1.16–1.35), PS (1.05–1.07), Nylon (1.14), Polycarbonate (1.20), Acrylic (1.15)

Why it matters: The Great Pacific Garbage Patch is dominated by floating HDPE, LDPE, and PP debris. PET bottles and PS foam often sink, ending up in the ocean floor.

Is It Nylon?

Look for a burnt‑wool smell, blue flame with a yellow tip, and molten droplets that stop when the flame is removed. A nylon sample will also sink due to its higher density.

For deeper insight, read our detailed guide on plastic types published on 10/15/21: our blog dated 10/15/21.

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