Narrow-Mouth Glass Bottles

A narrow mouth is a deliberate choice, not a cheaper one. The smaller opening means less liquid surface exposed to air, a smaller cap seal to fail, and far less chance of the contents slopping out when the bottle is carried or tipped.

Narrow or wide

Narrow-mouth bottles are for liquids: reagents, solvents, standards, samples that are poured. The restricted neck also makes them easier to pour from accurately, because the flow is controlled rather than a sheet.

Wide-mouth bottles are for anything that has to go in or out as a solid — powders, tablets, swabs, soil — or that needs to be reached into with a spatula. Trying to fill a narrow-mouth bottle with a powder is a lesson everyone learns once.

Neck finish matters

The neck finish, quoted as something like 20mm-400, states both the diameter and the thread form. A cap has to match both. A closure that seems to fit but was made for a different finish will seal against the wrong surface and will leak — usually in transit, in a box with other bottles.

Glass over plastic

Glass does not absorb, does not leach plasticiser and does not swell in solvents, so it is the right container for organic samples, standards that must not change, and anything held for a long time. It also breaks, so it belongs in a rack or a transport case, not loose in a bag.