Cosmetic Jars: What 30 g Actually Means, and Why Wall Thickness Sells
By Joe Joo · 8PCK · Shantou · Updated 26 October 2026
A “30 g jar” is named after the fill weight, not the volume — which is why two 30 g jars can look completely different on shelf. This page covers fill weight, single versus double wall, and how the cap decides the feel.
Cosmetic jars are sold by fill weight: 30 g, 50 g, 100 g. The number tells you how much product goes in, not how big the jar is. A 30 g jar in single-wall PET and a 30 g jar in double-wall PETG hold the same amount and read as two different price points.
That gap — same fill, different perceived value — is the whole game in skincare packaging.
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Single Wall vs Double Wall
A single-wall jar is one moulded piece: lighter, costs less, and is the standard for volume skincare. A double-wall jar has an outer shell and a separate inner cup, so the product never touches the decorated surface and the wall can be thick without using more resin than necessary.
Double wall is what makes a jar feel expensive. It is also what makes it heavier to ship, and the two parts have to be assembled — both of which show up in the unit price.
Why the Cap Decides the Feel
Buyers judge a jar by the lid: the sound it makes and the weight in the hand. A thin PP cap on a thick-wall jar feels wrong immediately. For premium lines the cap is often the heavier part — ABS or thick PP, sometimes with a metal-look insert.
If you are sampling, judge the jar with its cap on. Half the perceived quality is in the closure.
Threads, Refills and the EU Refill Push
A screw jar can be refilled only if the refill cup is designed for it; most double-wall jars are not. If refillability is part of the claim, say so at the brief stage — it changes both the mould and the packaging configuration.
Where Cosmetic Jars Leak, and It Is Usually the Liner
A cream jar that leaks in transit is rarely a mould problem. Three causes cover most of it.
Liner Incompatible With the Formula
Oil-based creams swell EPE liners; silicone liners cost more and resist. If the formula has a high oil phase, specify the liner with the jar.
Over-Torque at the Filling Line
A torque above the jar's spec distorts the liner and opens a gap on one side. Specify a torque range with the capping machine, not a 'tight' instruction.
Thread Depth on a Double-Wall Jar
Double-wall jars have an inner cup; the thread is on the outer shell. A liner that fits a single-wall jar may not sit flat on a double-wall rim.
Frosting, Spray Coat and What They Cost
Frosting is a surface treatment from 1,000 pcs and reads as soft-touch glass. Spray coat and metallising start at 3,000 and add 5-8 days. For a 30 g cream at launch volume, frosting plus label is usually the cheapest premium look.
Questions We Get on This
Is a 30 g jar the same as a 30 ml jar?
Not exactly. Grams measure fill weight, millilitres measure volume. A 30 g cream at typical density is close to 30 ml, but a light emulsion can be 35 ml in the same jar.
Can you print on a jar lid?
Yes — silkscreen or hot stamp on the lid top, at 1,000 and 3,000 pcs MOQ respectively.
What is the MOQ for a frosted jar?
1,000 pcs. Frosting is a surface treatment, not a colour, so it does not add a colour changeover.
Can the jar be made from recycled material?
PET and PETG can include recycled content; the percentage changes clarity and needs its own declaration. Ask for the grade before you promise a recycled claim.
What is a standard cosmetic jar size?
30 g, 50 g and 100 g by fill weight; 15 ml for samples and travel.
Do you supply the cap and liner?
Yes — screw lids with EPE, silicone or induction liners, tested on the jar.
Can the jar be frosted?
Yes, from 1,000 pcs. Frosting does not add a colour changeover.
Sizes That Fit This Guide
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