# Corn cob finishing media

Corn cob grit and treated finishing media, with supplier-specific grading, density, moisture and absorption bases.

Reviewed: 2026-10-29

Tags: abrasives, mass-finishing, drying, reference

## Identity and scope

GreenTru **2040** lists **35% on No. 30, 60% on No. 40 and 5% on No. 50**, with untapped bulk density **21–27 lb/ft³**. [GreenTru specifications][grading] Kramer’s finishing and drying grit uses the hard, woody part of the cob. [Kramer Corn Cob Media Grit][kramer]

GreenTru lists woody-ring 1014, 1420 and 2040 for tumbling and vibratory finishing. Its 1440PC and -40PC absorbents and carriers use pith, chaff and beewing material. [GreenTru product descriptions][products]

This reference covers supplied media and quantity interpretation. [Finishing process references](../../processes/finishing/index.md) covers the wider process context. [Walnut shell media](walnut-shell-media.md), loose mineral abrasive, preformed ceramic media, and finishing compounds have separate identities. A carrier granule and an abrasive or polishing agent added to that granule describe different constituents.

## Plain grit and treated formulations

Here, plain grit means the supplier's cob-grit product rather than a separately identified compound-treated formulation. The word does not establish analytical purity or the absence of every processing aid.

Kramer's Premium Treated Media family uses corn cob, walnut shell, or other bases with added abrasives, lubricants, binders, and polishing agents. The supplier describes dry tumbling without added water or separate compounds. The page does not identify every grade's base and complete ingredient concentrations. Its Pegco grade names and finishing factors therefore cannot establish that an individual product is corn-cob based or identify its abrasive chemistry. A formulation family is insufficient evidence for a particular treated grade. [Kramer Premium Treated Media][treated]

**Synthesis:** drying removes liquid from a part, while dry tumbling describes a finishing process without added water. Treated polishing media can contain process-active additions even though the carrier originated in a plant. Neither an organic label nor a natural-feedstock claim establishes complete chemistry, contamination-free media, or compatibility with a coating, metal, or cleanliness requirement.

## Supplier grades and particle distributions

Green Products' illustrative table names U.S. Standard screens and percentages of particles retained, without specifying a mass or particle-count basis. These rows retain every nonblank screen entry for each selected grade. [GreenTru specifications][grading]

| GreenTru grade | Retained on named screens | Untapped bulk density, lb/ft³ |
| --- | --- | --- |
| 1014 | No. 14: 80%; No. 20: 20% | 27 to 35 |
| 1420 | No. 20: 80%; No. 30: 20% | 23 to 33 |
| 2040 | No. 30: 35%; No. 40: 60%; No. 50: 5% | 21 to 27 |

The supplier's changeable, illustrative values are not exact specifications. Retained fractions are not cumulative percentages passing or guarantees of a bounded particle size. [GreenTru specifications][grading]

Kramer's current product table gives Medium 14/20 as 1.40 to 0.85 mm and Fine 20/40 as 0.85 to 0.42 mm. Its Extra Fine row says 30/80, 0.56 to 0.16 mm, while an image caption says 40/60 Extra Fine. Images are expressly for comparison. These are source-specific labels with an unresolved mismatch, not interchangeable sieve specifications. [Kramer grade table and captions][kramer]

**Synthesis:** a sieve opening is a passage dimension, not a measurement of every axis of an irregular granule. The supplier's grading basis, distribution, part openings, and separation screen all affect interpretation. A mesh label alone cannot prove that media will enter, leave, or avoid lodging in a particular feature. No universal mesh-to-surface-roughness relationship follows from these tables.

## Density, moisture, and composition bases

AGSCO's two-page Corn Cob Grit sheet, revised 2/5/2025, gives dry packing density as 16 to 35 lb/ft³. Its size table gives 27 to 35 lb/ft³ for Grit No. 1, 10-14 mesh, and 21 to 26 lb/ft³ for Grit No. 3, 20-40 mesh. It does not identify a tapped or untapped procedure. These values cannot silently replace GreenTru's explicitly untapped values. [AGSCO technical sheet][agsco]

The AGSCO sheet labels another property specific gravity but prints 1.0 to 1.2 g/cm³. Specific gravity is dimensionless, whereas g/cm³ is a density unit. The sheet leaves the measurement method and particle-volume basis unspecified. Its value is not a bulk-density conversion. The same sheet reports free moisture of 8.0% and an elemental analysis. Neither a moisture denominator nor test conditions are stated. An elemental analysis describes elements, not a complete molecular formulation or a contamination certificate. [AGSCO technical sheet][agsco]

GreenTru's grading page states a maximum moisture of 10%, without a wet-mass or dry-mass denominator or drying-test conditions. [GreenTru specifications][grading]

The following distinctions are arithmetic definitions, not supplier test methods:

| Quantity | Defined basis | Interpretation |
| --- | --- | --- |
| Bulk density | Sample mass divided by occupied bulk volume, including spaces between particles | Packing state matters. |
| Particle density | Particle mass divided by the specified particle volume | Pore treatment depends on the method. It does not include spaces between separate particles. |
| Wet-basis moisture fraction | Water mass divided by total moist sample mass | 8% means 8 kg water in 100 kg total sample. |
| Dry-basis moisture fraction | Water mass divided by dry solids mass | 8% means 8 kg water per 100 kg dry solids. |

**Hypothetical calculation:** 100 kg of media at an assumed 8% wet-basis moisture contains 8 kg of water and 92 kg of dry solids. Its dry-basis moisture is 8/92 × 100 = 8.70%. If 8% instead meant dry basis, 100 kg of total media would contain 100 × 0.08/1.08 = 7.41 kg of water. Neither interpretation assigns a basis to an unspecified supplier value. This calculation is not a drying target or treatment recipe.

## Absorption and process applicability

Green Products reports approximately one pound of water absorbed per pound of woody-ring grit, compared with about four pounds per pound of pith and chaff. Its product page separately reports approximately 4.5 times the product's own weight for 1440PC and -40PC. The descriptions concern different fractions or products. None states initial conditioning, contact duration, water temperature, drainage method, or whether the initial media mass is oven-dry or as supplied. [Green Products absorption description][absorption], [PC product descriptions][products]

**Synthesis:** liquid uptake divided by initial media mass is different from total wet mass divided by initial media mass. For a hypothetical 1 kg sample that takes up 1 kg of water without solids loss, uptake is 1 kg/kg and final mass is 2 kg. An equilibrium or unspecified uptake claim supplies no drying rate, remaining useful capacity, oil uptake, or behavior of already loaded media.

Kramer makes reuse conditional on contamination, particle breakdown, recovery, and surface requirements rather than a fixed cycle count. [Kramer reuse discussion][kramer] A generic cob description supplies no validated life, residue-free result, finish, processing time, temperature, speed, or universal substrate compatibility. Added compound, absorbed liquid, and material removed from parts can change the used media's composition. This is a process interpretation, not a characterization of any customer's media.

## Safety evidence and used-media limits

Kramer's Corn Cob Grit SDS has a printed revised date of 6/1/15. Its composition section says no hazardous components rather than providing a full ingredient inventory. It lists strong oxidizers as incompatible and limits its transport statement to products in their original form. These historical statements do not qualify current treated products or establish the chemistry of recovered media. [Kramer SDS, three pages][sds]

OSHA describes hazardous blasting dust as potentially originating from both abrasive and the underlying substrate or coating. Its combustible-dust overview explains that finely divided combustible material can become explosible under appropriate suspension and concentration conditions. Neither document supplies an explosibility measurement for the particular media discussed here. [OSHA abrasive-blasting fact sheet][osha-blast], [OSHA combustible-dust overview][osha-dust]

**Synthesis:** low dust, biodegradable, or natural descriptions do not establish harmless used-media dust, current workplace qualification, or an approved disposal route. An old SDS is not evidence of current standards compliance. The supplied formulation, its present documentation, and the actual material generated in use remain separate evidence questions.

## Sources and coverage limits

Reviewed 29 October 2026 PDT. Web pages are retrieval snapshots unless a printed version is identified. This reference does not establish customer capabilities, approved settings, lot acceptance, or a qualified cleaning process.

| Primary source | Coverage and version limit |
| --- | --- |
| [Kramer Corn Cob Media Grit][kramer] | Product description, current grade table, comparison captions, reuse discussion, and FAQs. Page displays October 7, 2015, but that date does not establish the age of every current passage. |
| [Kramer Premium Treated Media][treated] | Family description, grade tables and their stock-item footnotes, and FAQs. Page displays July 30, 2019. No grade-specific complete formulation is established. |
| [GreenTru products][products], [specifications][grading], and [absorption description][absorption] | Feedstock distinctions, the full illustrative grading table and caveats, and manufacturer uptake claims. No printed revision or complete absorption test method. |
| [AGSCO Corn Cob Grit technical sheet][agsco] | Both pages, including application matrix, size-density rows, typical properties, and elemental analysis. Printed revision 2/5/2025. Typical values are not lot certificates. |
| [Kramer Corn Cob Grit SDS][sds] | All three pages. Printed revision 6/1/15, retained as historical product-specific evidence. |
| [OSHA blasting fact sheet][osha-blast] and [combustible-dust overview][osha-dust] | Fact sheet DSG FS-3697, 09/2014, and an undated overview. General hazard context, not formulation certification or a process-specific dust test. |

Coverage does not include a current treated corn-cob grade's complete composition, specified particle-density method, conditioned absorption test, validated residue limit, or application-specific qualification.

[kramer]: https://kramerindustriesonline.com/product/corn-cob-blasting-media-grit/
[treated]: https://kramerindustriesonline.com/product/premium-treated-vibratory-tumbling-media/
[products]: https://www.greenproducts.com/greentru/corncob-products/
[grading]: https://www.greenproducts.com/greentru/corncob-products/product-specifications.aspx
[absorption]: https://www.greenproducts.com/greentru/why-corncob.aspx
[agsco]: https://www.agsco.com/assets/pdfs/Corn-Cob-Grit.pdf?r=false
[sds]: https://www.kramerindustriesonline.com/wp-content/uploads/corn_cob.pdf
[osha-blast]: https://www.osha.gov/sites/default/files/publications/OSHA3697.pdf
[osha-dust]: https://www.osha.gov/combustible-dust