Overfilled tins: the dome, the smeared lid and the fill weight to use instead

A convex pour plus about 10 percent thermal expansion pushes balm onto the lid. Fill weights by tin size, a levelling rescue and the pour that sets flat.

A tin that took its lid perfectly on the bench comes back from a customer with a greasy disc printed on the inside of the lid and a scuffed hollow where the surface used to be. Nothing has gone wrong chemically. The tin was filled to a volume it does not have, the contents grew when they got warm, and the only place for the extra to go was up. This page gives the fill weights that avoid it, the rescue for tins already filled, and the reason a domed pour is not the same thing as a full tin.

• Balm density: about 0.90 to 0.92 g/mL
• Headroom: 2 to 3 mm
• Expansion 20 to 60 C: 8 to 12%
• 1 oz tin: 26 to 28 g
• Fill by weight, not by eye

A 30 mL tin does not hold 30 g

The first error is a units error and it is extremely common. Container capacity is quoted in volume, batches are made and sold by weight, and balm is lighter than water. Vegetable oils sit at roughly 0.91 to 0.92 g/mL at 20 C in the Codex specifications for named oils, waxes and hard butters run higher in the solid state, and a set balm with air-free packing lands in the 0.90 to 0.92 g/mL band. Multiply volume by 0.90 and you have a conservative brim-full weight; the working figure used across this site is 0.92.

The second error is that nominal size means two different things. A tin sold as 30 mL is being described by something close to its brim volume. A tin sold as 1 oz is being described by its intended net contents, 28 g, which is a smaller number in millilitres. Suppliers use both conventions, sometimes in the same listing, and the gap between them is roughly the headroom you were meant to leave. That is why so many first batches fill neatly to the brim and then fail in a warm room.

Headroom in millimetres converts to grams through the internal diameter, and this is the calculation worth doing once for every tin you buy. A 60 mm internal diameter gives a cross section of 28.3 square centimetres, so 1 mm of depth is 2.8 mL, about 2.5 g of balm. A 45 mm tin gives 15.9 square centimetres, so 1 mm is 1.6 mL or about 1.4 g. In a wide shallow tin, three grams is the difference between a clean lid and a smeared one. The same conversion is what the batch calculator is doing when it turns a container count into a batch weight, and the format comparisons including fill weights per container are on the packaging guide.

The 8 to 12 percent nobody budgets for

Fats expand when they warm, and most of that expansion is not thermal expansion in the ordinary sense. It is the crystals melting.

Liquid oil alone is undramatic. Noureddini and colleagues (1992) measured the densities of the common vegetable oils against temperature and found a near linear fall of roughly 0.00065 g/mL per degree, so an oil at 0.917 g/mL at 20 C is near 0.891 at 60 C. That is about a 3 percent gain in volume across the whole 40 degree span. Nothing in a tin fails because of 3 percent.

The crystalline fraction is the larger term. A triglyceride in its stable crystal form is denser than the same triglyceride as a melt, and the specific volume change on melting runs to roughly 10 to 13 percent for the fats used in balms (Timms, 1985). So the total expansion depends on how much of your balm is solid to begin with, which is the quantity described on solid fat content. Work it through: a balm that is half crystalline at 20 C and fully molten at 60 C gains about 3 percent from the liquid plus half of 11 percent from the melting solids, which is 8 to 9 percent. A hard, wax-rich stick formula with a higher solid fraction sits at the top of the 8 to 12 percent band. A soft body balm at 25 percent solids is nearer 5 to 6 percent.

Translate that into the thing that touches the lid. A 1 oz tin filled 11 mm deep and warmed until it is fully molten rises by roughly 1 mm. That sounds trivial until you remember it is 1 mm of rise starting from a surface that was already domed and already brushing the lid. And the rise does not simply reverse: molten balm that has touched and wetted the lid stays there, and what drains back sets as a hollow with a raised rim.

A domed pour is not a full tin

Pour a balm into a tin and it does not sit flat. Surface tension pulls the melt into a slight dome once it is proud of the rim, and it will hold that dome as it sets because the balm becomes a solid before gravity can flatten it. Two things follow. The peak of a dome can be 1 to 2 mm above the average level, so a tin that is correct by weight can still be touching the lid at one point. And the volume in the dome is small: for a 60 mm tin, a 1.5 mm dome carries roughly 1.5 to 2 g, so you paid a lid smear for about 6 percent more product.

A dome also concentrates every later problem in one place. It is the first part to contact a warm lid, the first to be wiped flat by a sliding closure, and the point where any surface migration shows. If you want a genuinely fuller tin, use a larger tin. A convex fill is not extra generosity, it is a defect that happens to look generous on day one.

Pouring too cool makes the dome worse, because a melt near its setting point is already viscous and holds whatever shape it lands in. Pouring at the correct temperature, 60 to 68 C for tins, lets the surface level itself before it sets, which is one of several reasons the windows on pour temperatures matter more in a wide container than in a tube. Cold tins have the same effect locally: the balm skins where it touches the metal and freezes an uneven surface in place, and shrinkage away from the centre then produces the dips described on tunnelling and dips.

Which smear are you actually looking at

Balm on a lid has four common causes and they need different fixes, so identify it before you reprocess anything.

Rescue the tins you have already filled

Overfill is fully recoverable and does not need a batch remelt unless the tins are grossly over.

1. Scrape the lid, do not wash it. A dry lint-free cloth or a plastic scraper takes the film off. Water is the one thing that must not go into an anhydrous product, and a lid dried in a hurry carries it straight back in, which is how the problems on water contamination in balm start. If a lid needs more than wiping, use a little of the balm's own oil on the cloth, or high strength alcohol and let it flash off completely.
2. Weigh five tins before deciding anything. If they are within a gram or two of your target, the fault is the dome and not the weight, and levelling alone will fix it.
3. Warm the surface to about 40 C and let it level. A heat gun on low, held well back and kept moving, or a few minutes in a warm cabinet. You are melting the top millimetre so surface tension and gravity flatten it, not remelting the tin. Stand the tins level and leave them uncovered until fully set.
4. If they are genuinely over, remove 2 g from each. A warmed spoon lifts a clean scoop. Collect the removed balm in one vessel, and either remelt it into the next batch or use it for samples.
5. Check the declared weight before you take anything out. Removing 2 g from a tin labelled 30 g net leaves you short, which is a labelling problem rather than a cosmetic one. The net quantity rules are covered on labelling cosmetics in the UK and labelling cosmetics in the US.
6. Only remelt the batch if the tins are more than about 10 percent over. At that point levelling will not create enough headroom and you are better off emptying, reweighing and refilling. Warm the tins to 40 C first and the contents lift out in one disc.
7. Reweigh and relabel. Any tin that has had product removed or added should go back through the same check as a fresh one, and the batch record should say what happened. Format on batch records.

Slip, screw and sliding lids tolerate different fill heights

Headroom is measured to the sealing plane, and the sealing plane is in a different place for each closure. This is why the same 26 g fill can be perfect in one supplier's tin and a disaster in another's.

A slider tin is the one to watch, because it is usually the smallest and shallowest format in the range and its lid is the only one that moves across the product face in normal use. One millimetre proud is a permanent scuff after the first opening. Check the closure against the formula too: a soft balm in a slider looks worse for the same fill height than a firm one, because the lid gouges rather than glides, which is part of the wax level argument on balm too hard or too soft.

Fill by weight, into warm tins, and lid last

Every reliable filling operation, at any scale, weighs. Volume filling by eye is the root of the whole problem, because a maker judging by eye is judging against the rim, and the rim is exactly where the balm must not be.

1. Set the target fill weight once per tin type. Fill one tin to the brim with water, weigh it to get the brim volume in mL, multiply by 0.90, then subtract the headroom in grams using the diameter conversion above. Write the number on the shelf label for that tin.
2. Tare and check-weigh. Zero the scale with an empty tin on it, fill to the number, and spot check every tenth unit. A scale reading to 0.1 g is enough for tins; the calibration routine is on weighing and calibration.
3. Prewarm the tins to about 40 C. A low oven or a warming plate. This stops the pour skinning on contact with cold metal, and a surface that stays fluid for a few more seconds levels itself.
4. Pour into a level tray, not onto the bench. A baking tray on a levelled shelf keeps every tin in the batch at the same angle while it sets.
5. Leave the lids off until the balm is fully set and below 25 C. This is 30 to 60 minutes for a 1 oz tin. Lidding warm traps heat, dulls the surface and can condense moisture on the lid.
6. Do the heat check before you commit to a fill height. Put three filled and closed tins at 40 C for four hours, then cool them and open them. If the lid is clean, the fill height is right for a warm delivery van.

Above a few hundred units a piston or gravity filler set by weight removes the variability entirely, and the options are on filling equipment. The equivalent geometry problem in a twist-up tube, where the meniscus and the second top-up pour are the issue rather than a lid, is on filling lip balm tubes.

What a fill weight cannot fix

Fill height controls contact between the balm and the lid. It does not control anything else, and it is regularly blamed for faults that belong elsewhere. A balm that arrives soft enough to smear at a correct fill weight has a formula problem, and the answer is wax level and melting point rather than two fewer grams; the trade-offs are on shipping in hot weather. Oil on the lid with no loss of product level is sweating. Rust marks under the lid rim are a container and moisture problem, dealt with on rust spots on balm tins, and a lid that will not seat cleanly may simply be a poor mould, which is worth checking against a second supplier before you change a formula.

Two things this page cannot decide for you. The first is your actual density, because a balm heavy in butters and waxes runs higher than one that is mostly liquid oil, and the only way to know is to weigh a container of known volume filled with your own product. The second is your tins: brim volumes vary by a few millilitres between suppliers and sometimes between production runs of the same item, so the table above is a starting point and the water-fill measurement is the method. The decision rule is simple enough to keep on the wall. Set the fill so the set surface sits 2 to 3 mm below the sealing plane, weigh every unit to that number, and let the tin be a little less full than it could be. Nobody has ever returned a balm for being 2 g light. They return it for being smeared across the lid.

Reviewed and updated 6 September 2026. Spotted an error? Tell us and we will fix and log it.