Use Specific Gravity to Weigh an RTV Shot | RUUIPON

To weigh a *dump* shot into a finished well, multiply cavity volume (cm³) by the dump's specific gravity (g/cm³), then add the heel you will leave in the cup and the runner if you have one. That is not the same math as weighing *rubber* to build the mold (box minus master plus waste). Chocolate grams are not millilitres; pectin solids change density. Mix platinum 1:1 or 10:1 *by weight* when you pour the tool; don't use that ratio as the dump calculator. Food wells stay ungreased so a scale ticket isn't an oil film. We would not spec tin so a hobby cup mark "looks close enough."

RUUIPON quotes rubber by mold volume and can help you lock cavity ml for your dump 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 *part* shot weight is a steel-tool conversation at wydsilicone.com.

Does not apply when you meant RTV grams to fill a flask (volume calculator page), when mg-per-gummy is a formula claim (we don't dose), or when the well is still CAD-open and you want us to guess from a photo. CBD/THC: tooling only.

Two masses people mash together

Tool mass. Box − master + waste, × SG of platinum (~1.1 g/cm³ typical — use the TDS). Mix A/B by weight.

Dump mass. Cavity volume × SG of *your* dump + heel. Outer-row gummies often 3–6% heavy vs center when a loaded tray sags 0.5–1.5 mm. Lock CAD, then weigh.

Don't convert a 4.0 g target to "4.0 ml." Ask for density or we CAD a cavity and you witness-weigh.

ISO 3302-1 M2 is dimensional class, not a gram spec. Put grams on the RFQ as a fill target, not as a Shore.

flowchart TD
  A[Need a weight] --> B{Rubber for the tool, or dump into the well?}
  B -->|rubber| C[Box minus master plus waste × rubber SG]
  B -->|dump| D[Cavity ml × dump SG + heel]
  D --> E{Food?}
  E -->|yes| F[Dry well, no grease, no tin; witness weigh]
  E -->|craft resin| G[Resin TDS density; don't copy chocolate grams]

The photo that would prove the dump calc: graduated cavity or CAD volume callout, scale ticket, cup heel shown. A kitchen cup with ratio marks is the wrong photo.

Typical shop values

Caption: Typical shop values.

Heel, runners, and why cup marks lie

A 10–20% extra on small dump shots is common so the last cavity doesn't starve. That extra is not "free grams in the piece." Weigh finished dumps, not the cup. Scale d=0.1 g is a different page; here the principle is SG × volume.

Thixo in the *tool* doesn't change dump SG. Pigment in the *dump* does. Pigment in the tool shouldn't bleed into chocolate; if it does, recast, don't oil.

Density sources we accept versus kitchen guesses

Accept: dump TDS, a lab density the buyer already runs, or a witness-weigh of a CAD-locked cavity. Don't accept: "water is 1 so chocolate is 1," "the 1:1 platinum cup marks," "Amazon said 4 ml gummy."

Heel: leave it in the calc so operators don't scrape the cup into the last well with a metal tool that nicks a food lip. Waste 10–20% on small food shots is typical shop talk, not a warranty.

If CAD is in inches, lock units before volume. A 0.1 inch vs 0.1 mm mix-up wrecks grams more than shrink 0.1–0.3%.

Depositor vs flood-and-scrape: shot weight method still holds; the machine doesn't invent density. Outer-row 3–6% heavy is sag until proven otherwise — jacket/board, then CAD tweak ($50 if volumes change).

Craft PU: use PU SG, not chocolate. Don't share a well. Food: dry, no grease, no tin. Tooling only on actives.

Worked example (anonymized)

Buyer wanted 4.0 g pectin gummies, sent "4 ml cavities." Solids made density ≠ 1. We CAD'd cavities from a target after they sent density, $50 because volume was open, platinum ~25A sheet, witness weigh center vs edge, jacket to fight sag. Dry wells. MOQ 20.

If the depositor ticket and the scale ticket disagree, believe the scale on the piece, then look at sag, not at a new Shore tattoo.

Resin dice and chocolate bars that share artwork still need two density lines and two skins. A PU SG will wreck a gummy gram target if someone copies the cavity ml. Cabinets split.

One procurement mix-up

Using the platinum 1:1 ratio as the dump recipe. That's the tool. Dump SG is yours. Charge ≠ a nutrition label.

We would not recommend

We would not recommend cup-mark volume for 1:1 platinum *or* for chocolate grams.

We would not recommend greasing wells so pieces "weigh right."

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

We would not recommend treating mg actives as a cavity spec.

What to ask when you're buying

• Tool grams or dump grams — which shot?
• Dump density, or do we witness-weigh after CAD?
• Heel included in the kettle ticket?
• Sag/jacket so outer-row stays in band?
• Food docs vs craft resin density TDS?

RFQ copy-pack

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

RUUIPON SG / shot-weight RFQ Shot: tool rubber / dump into well Dump: food / PU / epoxy; density if known Target grams or ml Heel / runner yes / no Qty: witness / MOQ 20 CAD: $50 3D if cavity volume still open

Matched next step: say whether you are weighing rubber or dump, and send density if you have it. We CAD volumes and witness-weigh. We will not oil chocolate to hit a gram. Prototype 3–7 business days after CAD lock. MOQ 20 per design.

Related: silicone volume calculator, cavity count vs piece weight, food-grade molds, contact.

Witness weigh: center vs edge grams, density source named, heel not scraped with metal into a food well. Lock units before CAD lock.

Send density or allow a witness-weigh after CAD lock. Do not convert millilitres to grams with a kitchen 1.0 guess on couverture or pectin.

A 1:1 platinum mix by weight for the tool never sets the dump grams. Write two lines on the RFQ: rubber mix, dump SG. Food wells dry. No tin. No cup marks on couverture.

If the first witness is light, check heel and sag before you open CAD. If it is heavy on the outer row only, jacket first. USD $50 when cavity millilitres must actually move. MOQ 20 after the weigh.

FAQ

Is 1 ml of chocolate 1 g? Not reliably. Use density and witness-weigh. Don't grease the well to "correct" grams.

Can I use the platinum SG for my PU dump? No. Different liquid. TDS of the dump.

Does shrink 0.1–0.3% change dump grams? Slightly on the tool. Your fill target is still a weigh.

If outer row is heavy, do I recast smaller edge cavities? Usually jacket the sag first. CAD $50 if we then tweak volumes.

Is mg-per-gummy a cavity field? No. Formula. Cavity is volume/grams of the piece, tooling only.