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11oz · 15oz
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Why does a squeezed balloon push back harder? Boylina feels the pressure. Boyle’s law, P1V1 = P2V2, says that for a fixed amount of gas at constant temperature, halving the volume doubles the pressure. Robert Boyle published it in 1662, and divers still plan around it. Pixel-art black ceramic mug in 11 or 15 oz; equation, symbols and sources in the physics panel below.

Size

Details

Size & material11oz · 15oz

Black glossy ceramic mug with a C-handle. Lead- and BPA-free.

  • 11oz: 0.33 l
  • 15oz: 0.44 l
CareDishwasher & microwave safe

Dishwasher safe (top rack) or hand wash. Microwave safe.

ShippingFree US

Free US shipping. $10 flat shipping outside the US.

Made to order: about 10 days of production and handling before it ships.

Delivery times & where we ship

Returns & replacements21 days

Every item is printed to order, so we can’t accept returns or exchanges for change of mind, or if you ordered the wrong size or colour.

Print defect, misprint, damage or the wrong item? We’ll send a free replacement, or a refund if you prefer. Report it within 21 days of delivery with a photo; no need to send it back.

Full refund & replacement policy

The physics

Boylina has a fixed amount of gas inside her, and squeezing her is a bad idea.

Robert Boyle published the law in 1662: for a fixed amount of gas at constant temperature, pressure times volume stays the same. Halve the volume and the pressure doubles. Edme Mariotte found the same relation independently in 1676.

SQUEEZE ME. I PUSH HARDER. The molecules have less room, so they hit each unit of wall more often. A bicycle pump gets harder to push as you compress the air in it. Divers plan around the same rule: as water pressure rises with depth, the air in their lungs and equipment is squeezed into a smaller volume, and it expands again on the way up.

Use absolute pressure, not a gauge reading, and keep the temperature steady. Real gases follow the law closely at ordinary pressures and drift from it when squeezed hard.

Boylina is not difficult. She simply keeps the product constant.

Equations

\[P_1V_1 = P_2V_2\]
\[PV = \text{const}\quad (\text{fixed } T,\ n)\]
Symbols
SymbolMeaningUnit
\(P_1, P_2\) absolute pressure before and after \(\mathrm{Pa}\)
\(V_1, V_2\) volume before and after \(\mathrm{m³}\)
\(T\) absolute temperature (held fixed) \(\mathrm{K}\)
\(n\) amount of gas (held fixed) \(\mathrm{mol}\)
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