Custom Logos on RTV Silicone Molds: Depth and Face

If you're putting a custom logo on an RTV silicone mold, it's a fill problem, a tear problem, and a master-finish problem. Raised or recessed art will copy only if the rubber can enter the serifs and peel without tearing them. A platinum RTV cavity peels a mark that an LSR steel tool must eject — and that steel is a different WYD-style quote for a molded *part*. Pad-print is a third process that doesn't live in the cavity at all. If the RFQ says "add our logo" with a PNG and no depth, the shop will guess, and first article will be a debate about pride.

This is how to put a mark on a custom RTV tool so it fills, reads, and lasts. It isn't a branding essay.

Raised, recessed, and pad-print are three different tools

Recessed in the casting (raised on the master / raised in the cavity). The dump must fill a pocket in the RTV. Fine serifs starve in high-viscosity HCR compression more readily than in soft platinum RTV — don't copy an RTV prototype's hairline into an HCR *part* tool and then complain. Recessed marks in chocolate or gummy hide wear from knives and washers.

Raised in the casting (sunk in the cavity). The mark stands up. It reads well on a soft dump and takes abrasion. On a sealing face it leaks. On a stretchy undercut it can tear a 10A–20A lip.

Pad-print or screen. Ink on a finished *part* or on a carton. The RTV tool doesn't carry the art, except maybe a nest. Don't draw print as engraved master. Don't call pad-print "embossed."

Laser or ink after molding is another family. Useful for date codes that change. Useless as a substitute for a molded-in brand that must survive a dishwasher without ink.

Pick one on the 2D. Mixing "molded-in look, but we will print if it is hard" is how you pay for both and like neither.

Depth and draft of a mark the rubber will actually fill

Hairlines that look sharp in Illustrator become trenches the rubber or the dump won't enter. Give serifs width, depth, and a few degrees of draft so the mark strips. Exact numbers belong to the grade and the process, which is why a shop should mark the art, not why you should send a 0.1 mm stroke and hope.

Soft platinum RTV copies fine detail that millable HCR of the same envelope may starve, because the peel is flexible. That isn't a reason to specify RTV solely for a logo on a future *part*. It's a reason not to treat the RTV witness as production HCR or LSR data.

Undercut in a serif (a "V" that closes) will tear a 10A–20A lip. Fillet the root. Place the mark on a face that doesn't stretch around a core. Keep it off the parting land or the shut will shear the letters.

Logo on a flexible RTV mold versus on an LSR steel cavity

On RTV (this site), the art is on the master. Print quality, sanding, and inhibition decide the cavity. A sticky SLA master that inhibits platinum will give you a sticky logo pocket. Tin-cure RTV may copy a dirty master and then keep shrinking until the mark distorts. If the RTV mold *is* the product (a chocolate or gummy tray with a brand in the pocket), food-contact is a grade path (FDA 21 CFR 177.2600, LFGB), not a font choice.

On LSR steel, the art is electrodes, engraving, or an insert. Inserts let you swap brands without recutting the block. They also create a witness line if the insert is proud. Heat and polish around the letters affect stick: a mirror-polished logo well can vacuum-lock a soft part. Different RFQ.

On HCR compression, think fill from a charge. A logo far from the preform may starve. Different RFQ.

Wear, polish, and when the mark disappears

RTV cavities wear by tear. Sharp letter roots are tear starters. A mold used for resin or chocolate will dull differently than a mold used for abrasive-filled casting. Don't paste a cycle-life number. Specify duty and inspect the letters. A recast against the unsanded master is how you restore the mark; sanding the master "to clean it up" is how you lose it.

Steel logos wear from abrasive compounds, from texture blasting that was done after the letters, and from polishing that kisses the high points. That's the parts conversation. Neither lasts if someone "just polishes it again" every time flash appears.

If the brand must outlive a season of dumps, keep the master, recast the skin, or pad-print if the art is too fine to peel. Tiny raised serifs on a 70A spatula face are a wish on a *part* tool, not this tray.

Artwork files shops can cut without a redraw

Send vectors (AI, SVG, DXF) with outlined fonts, a stated depth, a stated raised-or-recessed condition, and a placement on the 3D. Bitmap logos become a redraw you'll hate. Pantone is color of the *dump* or the carton, not of the master.

Legal marks (®, ™) need enough width to fill. Chinese-character fine strokes need the same honesty as serif English. If the art can't survive a 0.3 mm minimum feature conversation, it's print, not mold.

China shops will cut the bitmap into a master if you insist. You'll then argue about missing dots. Put the vector and the depth on the freeze package with the rest of the custom mold. The logo is a cavity feature. Treat it like one, or don't mold it in.

ISO 3302-1 might class a logo *depth* on a rubber article drawing. It's a drawing class, not a promise the serif will fill. Don't write "ISO 3302 high precision logo" as a substitute for width and draft.

Common mix-up: a PNG titled "emboss this"

A lot of RFQs treat a screenshot as CAM-ready art. In the shop that usually means someone traces a bitmap, guesses 0.2 mm, and parks it on the shut. Send outlined vectors, depth, face, and raised-or-recessed. Then the pour can copy it.

What to ask when you're buying

• Raised or recessed in the pocket, depth, which face?
• Vectors with outlined fonts, or are we redrawing a PNG?
• Off the parting and off the sealing lip?
• Platinum or tin — will tin movement distort the mark in storage?
• Recast path if the letters tear: same unsanded master?

Worked example: 0.4 mm recessed brand on an 8-cavity bar

A confectionery line wanted an 8-cavity bar, 120 x 60 x 12 mm, food-contact, about 500 pours a month, recessed brand 0.4 mm in the pocket, serifs drafted. The art went on a CNC (or fully post-cured SLA) master, platinum 10A–20A skin, jacket so the sheet wouldn't sag 0.5–1.5 mm and smear the mark on the outer row. A PNG parked on the shut would have sheared. A parallel LSR engraving quote doesn't dump chocolate.

When this logo advice does not apply

If the mark is pad-print on a catalog tray whose pocket already matches, don't buy a custom master. If you need the logo on a vulcanized silicone *part*, open an HCR or LSR RFQ — different WYD-style quote. A one-off resin figurine can take a shallow peel mark without production draft. Geometry can override quantity: a negative-draft letter at 80 pours still needs the split off the face.

Related reading: design guide, common design mistakes, what a custom mold is, custom RTV molds.

Logo pack to copy onto the freeze

Copy this. A PNG without these lines isn't a mark.

• Process: platinum or tin RTV (art lives on the master)
• Outlined vectors; min feature width; depth
• Raised or recessed in the pocket; which face
• Off parting; off sealing lip
• Recast against unsanded master if letters tear
• Food-contact path if the tray is sold as food-contact

Send the STEP, outlined logo, depth, and dump material. We'll mark whether the serif will peel, whether it belongs on the master, or whether it's print.

We would not recommend parking the brand on the shut

We would not recommend a 0.1 mm hairline on a 10A–20A lip. We would not raise Shore A first to "hold the logo." We would not treat an RTV peel as proof an HCR charge will fill the same serif. We would not sand the master to "clean up" letters you expect to recast.

RUUIPON Mold Structure Decision: art on the master, off the parting. Flat back? open-back. Negative-draft letter that won't peel? move the split or add a core. Soft 10A–20A or wet dump? mother mold so the mark doesn't smear when the sheet sags.

flowchart TD
  A[How will the logo live?] --> B{Molded-in on RTV?}
  B -->|yes| C[Vectors plus depth on the master]
  C --> D{Peel without tearing 10A-20A?}
  D -->|no| E[Widen serifs, fillet, or move split]
  D -->|yes| F[Freeze face; keep unsanded master]
  B -->|pad-print| G[Don't engrave the master]
  B -->|on an LSR or HCR part| H[Stop: different part RFQ]

Typical shop values

Caption: Typical shop values (not a named lot).

| Item | Typical shop value | | --- | --- | | Mix | Platinum 1:1 or 10:1; vacuum degas | | Cavity Shore | 10A–20A skin with jacket | | Platinum shrink | About 0.1–0.3%; tin movement distorts fine marks in storage | | Loaded-tray edge sag without a jacket | About 0.5–1.5 mm — smears outer-row logos | | Min feature conversation | About 0.3 mm width; 0.4 mm recessed brand is a common food-mold start | | 8-cavity 120 x 60 x 12 mm bar | About 500 pours/month is a common first band |

FAQ

Can I send a PNG of my logo for a custom silicone mold? You can, and the shop will redraw it. Send outlined vectors with depth and raised-or-recessed stated. Bitmaps become arguments about missing serifs.

Will a logo that looked perfect in a platinum RTV prototype copy in HCR compression? Not automatically. RTV peels fine detail that millable HCR may starve. Recut depth and width for the production *part* process, or stay on RTV if the tray is the product.

Should a logo sit on the sealing lip so customers always see it? No. Marks on sealing faces leak or print into the mate. Put the brand on a free face, or print it after molding.

Is pad-print cheaper than molding the logo in? Often, when the art changes or is too fine to fill. It's a different process with ink durability questions. It isn't a molded-in brand.

Do food-contact rules change if I add a molded logo? The standard is still the grade and the article (FDA 21 CFR 177.2600, LFGB). The logo does add crevices to clean. Design depth so the pocket washes, and don't put the mark in a dirt trap.