How to Measure Shore A on an RTV Tray Face | RUUIPON

A Shore A number on an RTV tray is only as honest as the coupon you stuck the durometer on. A 3 mm lip reads softer than a 12 mm block of the same pour. A dusty, greasy, or dummy-backed well lies. ASTM-style practice wants adequate thickness, a specified dwell, and more than one spot. We quote a band — 10A–20A gloves, 20A–40A food trays as the RFQ needs — not a fake lot reading. Fill the empty table on your bench. Don't tattoo "20A" on a PO because a catalog icon said so. Food wells stay ungreased while you measure; oil drops the reading and films chocolate.

RUUIPON pours to a named band in Bao'an since 2018. Prototype 3–7 business days after CAD lock. MOQ 20 pieces per design. USD $50 when CAD scope applies. [email protected] · +86 135 3006 2969. LSR *parts* have their own Shore conversation at wydsilicone.com.

Does not apply when you meant ISO 3302-1 dimensional class (that's not hardness), when you are measuring HCR post-cured *parts*, or when the face is tacky from inhibition (scrap). Don't treat a durometer as 177.2600.

Method, not a result we invent

1. Use a Shore A durometer in calibration.
2. Measure on a stack or a coupon at least as thick as the instrument's practice — not on a 2 mm lip in air. Back the tray with a rigid plate.
3. Wait the dwell the instrument expects; don't bounce.
4. Three spots: center, edge, jacket-side if the glove varies.
5. Record room temperature. Cold trays read harder.
6. Caption your sheet Typical shop values until you have a named method. We will not write "we measured lot #…"

Empty table you copy:

Caption: Method table — fill on the bench; not a factory lab report.

Raising Shore to fight stick, sag, or ozone without this table is how you lock a hook. Structure Decision first.

flowchart TD
  A[Need a Shore number] --> B{Coupon thick enough, rigid back, clean dry face?}
  B -->|no thin lip in air| C[Don't record — stack or pour a coupon]
  B -->|yes| D[Three spots, dwell, temp]
  D --> E{Food well oiled?}
  E -->|yes| F[Wipe is not enough for food — recast if you greased chocolate]
  E -->|no| G[Band vs RFQ; don't chase 1A]

The photo that would prove the method: durometer on a stacked coupon, ruler for thickness, three marks. A catalog 20A icon is not that photo.

Typical shop values

Caption: Typical shop values.

Why the lip lies and the coupon doesn't

Durometer feet sink in thin sections and read the bench. That's why sag 0.5–1.5 mm and "the edge feels soft" are not the same as a 5A shift in the rubber. Pigment loading can shift hardness; measure after mix, not from the paste jar. Thixo in a glove can read differently than a pour-on block of the same grade — sequence, not magic.

ISO 3302-1 M2 stays on the drawing for dimensions. Don't write Shore in the tolerance block as if it were M2.

Temperature, dwell, and the greasy-foot lie

A tray from a 4 °C fridge reads harder; a tray from a 40 °C car reads softer. Write temperature on the method sheet. Dwell: if you bounce the durometer you are measuring your wrist. Three spots: if edge and center disagree by a wide band, you are seeing thickness/sag, not two rubbers. Pour a coupon.

Greasy foot: food oil, hairspray, talc, dummy dust. Clean a *craft* coupon; recast a food well you oiled to "help Shore." We would not. No tin.

Don't average a 12A lip with a 28A coupon and write 20A on the traveler. Report the coupon as the grade check and the lip as a geometry note.

If you need 10A–20A to peel and 30A to survive a spatula, you need a finger tab and a SOP, not a compromise 25A that does neither. Structure Decision plus method table.

LSR parts on steel have different Shore methods and shrink 2–3%; don't paste those onto an RTV tray RFQ. Route parts to wydsilicone.com.

Worked example (anonymized)

Buyer said a gummy sheet "wasn't 20A" because a pen-type durometer on a 3 mm lip read 12A. We poured a 12 mm coupon from the same batch, three spots in band, kept the sheet. No recast, no $50 CAD. Told them to stop oiling the lip before measuring. MOQ 20 unchanged.

Pen-type pocket durometers are worse on thin lips than a stand unit on a coupon. If the RFQ lives on a pocket pen, say so; we will still pour a coupon.

A jacketed 15A glove can feel "firm" in the mother and still be 15A on a coupon. Don't raise Shore because the jacket fooled your thumb.

One procurement mix-up

A marketplace "20A food grade" icon as the RFQ. Band plus method plus platinum vs tin. Charge ≠ a single-point reading on a greasy lip.

We would not recommend

We would not recommend official readings on a 2 mm lip in air.

We would not recommend oiling a food well to "stabilize" Shore.

We would not recommend chasing 1A with a new CAD fee.

We would not recommend tin because a hobby durometer liked it.

What to ask when you're buying

• Band, not a tattooed integer?
• Coupon thickness and who measures?
• Food well stays dry during QC?
• Shore vs sag vs stick — which problem?
• Jacket if the glove must stay 10A–20A?

RFQ copy-pack

Send to [email protected] · +86 135 3006 2969 · Xinhe Blvd, Shajing, Bao'an.

RUUIPON Shore-A method RFQ Target band: 10A–20A / 20A–40A / other Dump: food / craft Photo of how you currently measure Want a 12 mm coupon poured? yes / no Qty: witness / MOQ 20 CAD: locked / $50 3D if geometry, not Shore, must move

Matched next step: send how you measure today. We pour coupons and quote bands. We will not oil chocolate to make a durometer happy. Prototype 3–7 business days after CAD lock. MOQ 20 per design.

Related: Shore 10A vs 30A, Shore A gummy resin concrete, food-grade molds, contact.

Witness coupon: 12 mm thick, three spots in band, temperature written, food lip not used as the official number. Keep the empty table on the traveler.

Copy the empty method table onto the traveler before first article. We will not accept a single greasy-lip reading as a reject of a locked CAD.

Thumb-flex is not a durometer. Use the coupon.

Record the instrument.

FAQ

Why did the edge read softer than the drawing? Thin section and sag, or a dirty foot. Stack a coupon.

Does platinum vs tin change Shore more than method? Both matter. Method first. Tin still isn't food.

Can I convert Shore A to "stiffness of the dump"? No. Dump stiffness is formula. Shore is the tool.

Will a harder reading mean longer PU life? Not if the failure is exotherm or a hook. Confirm the empty well.

Do I pay $50 CAD to change Shore only? Usually no. Shore is a mix/grade note. $50 when geometry is open.