Sandblast stencil for headstones: thickness, liners, cuts

Every sandblasted letter on a headstone starts as a hole in a sheet of rubber. The sandblast stencil decides how crisp the edges are, whether small counters survive the blast, and whether the job lines up with the lettering already on the stone. Pick the wrong one for your cutter or your surface and you find out the expensive way, halfway through a blast.

This guide is for monument shops and cemetery lettering crews. It covers what monument stencil is made of, how thick it runs, single versus double liner, which punch format fits which plotter, fillers, and why the cut file matters as much as the rubber.

What a monument sandblast stencil is

A monument stencil is a sheet of rubber with a pressure-sensitive adhesive on one side and a release liner protecting it. You cut the letters and designs out of the rubber, weed the pieces you want blasted, apply the stencil to the stone, and blast. The rubber absorbs the abrasive while the exposed stone is cut away.

3M describes its monument stencils as tan rubber with a rubber adhesive, and notes that the tan backing "takes distinct carbon transfer so cut lines show up clearly" for hand cutting (Granite Sales & Supply, 3M page). U-Blast says its monument stencils are made from a synthetic rubber designed to balance flexibility and strength (U-Blast). Anchor's newer 113 style uses a rubber-based adhesive under a clear polyester liner (Miles Supply).

How thick is sandblast stencil?

Monument stencil thickness is quoted in mils (thousandths of an inch). The published numbers for common monument products sit between about 36 and 48 mil, roughly 0.9 to 1.2 mm:

• 3M 519Y, 519YT and 519YS: 48.0 mil (1.2 mm), double liner.
• 3M 520T and 520S: 45.0 mil (1.1 mm), single liner.
• 3M 1532 family: 37.0 mil (0.94 mm), single liner, factory order only.
• Anchor 124: 48 mil. Anchor 129Y: 45 mil. Anchor 125: 36 mil (high tack, made for raw wood).

The 3M figures come from the Granite Sales & Supply product page; the Anchor figures come from the Anchor stencil guidelines sheet published by Miles Supply. For comparison, Anchor's 128 is an 18-mil hand-cut stencil aimed at glass etching, light stone, tile and acrylic, which shows how much thinner a stencil built for shallow work can be.

Distributor pages can lag behind current data sheets, so confirm the exact product and thickness with your supplier before you reorder.

Single liner or double liner

This is the choice that most affects how the stencil gets from the cutter to the stone.

Double liner stencils add a thin film inside the sandwich. On Anchor's 129, a 2-mil polyester film between the outside adhesive and the rubber "holds centers in place while transferring stencil from computer to granite or marble" (Anchor page). That matters for letters with counters, like O, A, R and 8: the islands in the middle stay put when you lift the stencil off the cutter. 3M's 519Y family is a double liner design too.

Stencils without that inner film need more handling. For Anchor's 117 and 158, the Anchor page is clear: after cutting, the centers have to be taped before the stencil goes to the stone. 3M's 520 series and Anchor's 113 are single liner computer stencils. Miles Supply describes the 113 as intended to replace 3M's 520.

Anchor also makes "Y" versions of several styles (123Y, 124Y, 129Y, 154Y) with a yellow 2-mil film between the adhesive and the rubber, so you can spot any residue left on the stone after blasting.

Match the stencil to your cutter

Computer stencil is sold pre-punched for specific feed systems, and the wrong punch simply won't track. The Anchor and 3M listings sort into four groups:

1. Slot punch, for Gerber. Anchor 113S (listed as "Gerber slot"), 3M 519YPS (sold as "Gerber compatible") and 3M's slot punched 519YS and 520S.
2. IBM pattern, 1/2 inch on center. Anchor 154 and 113T, 3M 519YPT. The Anchor page notes the 154 will not work on large pin cutters.
3. Large pin 30 inch plotters. Anchor 192Y and the 30 inch 124 and 117.
4. Friction fed. Anchor 153 has its rubber trimmed back half an inch on each edge so the pinch wheels clamp the 5-mil polyester liner. No holes are needed.

Why does so much monument work still run on sprocket-fed Gerber plotters? The Plotter Doctor, which refurbishes them, gives two reasons. Tractor feed locks the rubber into sprockets on both sides so it "cannot drift or skew the cut" over a large area. And Gerber GS and HS heads are tangential: a motor turns the blade, which in thick material "will more accurately cut corners and follow curves" than a free-swiveling drag knife (The Plotter Doctor). They also note the faster HS series has to be slowed down to cut stencil, and that Gerber plotters are no longer made.

Fillers, tack and the stone surface

The stencil's own adhesive is only half the bond. Monument stencil is often paired with a filler, a brushed-on coating that helps the rubber grip the stone.

• 3M Stencil Filler 2 is for smooth or polished surfaces. Filler 3 is the same idea for axed or frosted surfaces.
• Anchor Filler 211 is medium tack, matched to stencils 111, 112, 117, 153, 157 and 158. Anchor Filler 223 is low tack, for 123, 124, 154 and 129.
• On polished stone Anchor recommends a light coat. On frosted, axed or steeled surfaces, two coats.
• Anchor Filler 333 is water based, works with all Anchor stencil and washes off with soap and water. It usually dries in about 20 minutes, turning from milky blue-white to a slightly amber clear when it's ready.

For cemetery lettering and flat markers, 3M lists an adhesive transfer tape that can be used in place of filler. It sticks to the stencil, so it comes off with it.

One caution from the Anchor sheet is worth repeating: the high-tack styles (116, 125, 155) are aggressive, are not recommended for some woods without testing a sample, and are not for pre-painted, pretreated or glass surfaces. Conditions matter too. U-Blast positions its UB2 for hot conditions and double process work, where you need to remove or shift a design between passes.

The cut file matters as much as the rubber

A tangential knife can only follow the path it's given. If a letter's curves arrive as hundreds of short straight segments, the knife steps from corner to corner, and on thick rubber those facets can show up as a rough edge on the stone. If the outline is open, or the counter of an A or R is missing, weeding goes wrong before the blast even starts.

That's why Monumize writes Gerber OMEGA-ready DXF files the way it does: R12 DXF with true arcs on closed polylines, counters intact, no live fonts, at 1:1 in inches. The same outline also comes as EPS, PLT, SVG and a 1:1 PDF, so it fits whatever your cutter software reads. You can check our sample files in your own setup before you spend anything.

Where this pays off most is adding a final date to an existing stone. The new stencil has to match lettering that was cut years ago, often by another shop. Monumize measures the existing letters from a phone photo and suggests a matching font, height and spacing, and you get a to-scale cut file for $49 per job. Our post on matching headstone lettering for a final date and the headstone fonts guide cover the matching side. How it works walks through the steps.

A quick checklist before you order stencil

• Thickness checked against the data sheet. Common monument stencils run 36 to 48 mil.
• Double liner if you cut a lot of counters and don't want to tape centers.
• Punch format matches your cutter: Gerber slot, IBM 1/2 inch, large pin or friction fed.
• Filler matched to the stencil's tack and the stone's finish.
• Current data sheet from your supplier, not an old product list.
• A clean vector cut file with true curves and closed outlines.

If you run a shop or a cemetery lettering crew, see Monumize for monument dealers or compare it with sandblasting versus laser etching if you're weighing methods.

Sources

• Granite Sales & Supply, 3M Scotch Brand Monument Stencils and Fillers: 3M thickness, liner and feed formats, fillers, transfer tape.
• Granite Sales & Supply, Intertape Anchor Stencil and Fillers: Anchor styles, inner film, punch formats, fillers and cautions.
• Miles Supply, Anchor Sandblast Stencil guidelines sheet: Anchor average thickness in mils.
• Miles Supply, Anchor Monument Sandblast Stencil Info Update: Anchor 113 single liner stencil.
• U-Blast, Monument stencils: synthetic rubber, single and double process, UB2.
• The Plotter Doctor, Monument Equipment and Software: tangential cutting and tractor feed on Gerber plotters.