Mesh size and particle size: reading 8x30 on a carbon sheet
Two carbons can have the same iodine number and still behave very differently in a vessel, because their grains are different sizes. Grain size is written on the sheet as a mesh range, and mesh size is the figure buyers most often copy without understanding. This note explains how to read it, what it changes in practice and what to say when you buy charcoal powder to activate.
What a mesh number is
Mesh size is a count of the openings per linear inch in a sieve. A bigger mesh number means a finer sieve and smaller grains. Grains are sorted by passing them through two sieves: they must go through the first and stay on the second. A range like 8x30 therefore means the grains passed an 8-mesh sieve and were held back by a 30-mesh sieve. In plain terms, the grains lie between the two openings.
Sheets we have read list ranges such as 4x8, 6x12, 8x16, 8x30, 12x40 and 20x50 for granular grades. These come from one supplier’s table, so treat them as examples of the notation, not as a standard list. The sieve series (US or another) should be named on the sheet. If it is not, ask.
Granular, powder and the grey zone
Granular carbon is retained on the coarser sieves of that series and is used where a bed of grains sits in a vessel and liquid or gas flows through it. Powdered carbon is much finer and is dosed into a liquid, then removed again. Between them is a grey zone where words differ by supplier. For that reason the mesh range is a better description than the word “granular” or “powder”.
What mesh size changes
- Flow and pressure drop. Finer grains pack tighter, so liquid or gas needs more pressure to pass through a bed. Coarser grains pass it with less pressure.
- Speed of uptake. Finer grains reach balance with the liquid sooner because the way into each grain is shorter. Coarser grains are slower.
- Handling. Fine material makes dust and sticks. Coarse material pours and stores more easily.
- Loss in service. Grains that break into fines are carried away or clog a bed. This is where hardness comes in, and it is why a sheet should carry both mesh and hardness.
None of this ranks one size above another. It means the right size follows from the equipment and the job.
The spread matters as much as the range
A sheet that says 8x30 should also say how much of the lot lies outside that range. Two lots can carry the same label while one holds a few per cent of fines and the other many more. Ask for the share above the top size and below the bottom size, and for the sieve analysis behind it. A tight spread behaves more predictably in a bed.
Buying charcoal powder to activate
When the starting material is charcoal powder, the question flips. You are not choosing the final grain size of a carbon. You are choosing the fineness of the feed that your line will process. Kora supplies powder milled from its shell charcoal with the mesh made to order, and publishes a moisture limit but no mesh range. So the mesh size is something you tell Kora, not something you read on a sheet.
To get a useful answer, send:
- The mesh or size range your process takes, and the sieve series it refers to.
- The share you can accept outside that range.
- Whether you need the powder dry, and the moisture you can accept.
- The packing you prefer, which for powder is a lined jumbo bag or a 25 kg sack.
If you do not know your range yet, say what kind of equipment you run and we will discuss what is possible. Be ready for the answer that the powder size also depends on the mill and the hardness of the charcoal, which is a property Kora does not yet publish.
Using the product page
The shell charcoal for activation page lists what Kora prints about its lump and powder, and which rows are still empty. Read it before you write the size line of your request.
A short checklist
- Name the sieve series next to every mesh range.
- Ask for the share outside the stated range.
- Pair the mesh size with a hardness figure.
- For powder feed, state the range your process takes before you ask for a price.
- Treat a word such as “granular” as a hint, never as a specification.
Send us the size you need
If you are working out the fineness for a feed, or reading a mesh range on a sheet and want a second look, write to us through the contact page. Give the equipment type, the mesh range and the volume you expect. We reply within two business days and tell you plainly what Kora can and cannot state.
Questions buyers ask
What does 8x30 mean on an activated carbon data sheet?
The grains went through an 8-mesh sieve and were held back by a 30-mesh sieve, so their size sits between those two openings. Mesh counts openings per linear inch, so a higher number means smaller grains. Ask which sieve series the sheet uses.
Does finer carbon work faster than coarse carbon?
Finer grains reach balance with the liquid sooner because the way into each grain is shorter. They also pack tighter, need more pressure to push liquid or gas through a bed, and make dust. Neither size is better; the right one follows from your equipment and job.
What should I tell Kora when I want charcoal powder to activate?
Send the mesh range and sieve series your process takes, the share you can accept outside that range, whether the powder must be dry and your moisture limit, and your preferred packing: a lined jumbo bag or a 25 kg sack. Kora makes the mesh to order and prints no mesh range.
Why is a mesh range alone not enough to describe a carbon?
Two lots can both be labelled 8x30 while one holds a few per cent of fines and the other many more. Ask for the share above the top size and below the bottom size, with the sieve analysis behind it, and read hardness beside mesh because soft grains break into fines.