The Stencil Lab
Every design gets measured before we publish it. Here is exactly what we measure, what the three-bar meter means, and what we do not claim.
We rate difficulty by measuring the artwork, not by carving pumpkins. Each design is turned into a black-and-white mask at 200 dots per inch, then a program measures the shapes: how many separate holes there are, how thin the strips of skin between them get, and whether any piece is left floating with nothing holding it. Six of those measures feed a score, and the score sets Easy, Medium or Advanced. No pumpkins were carved to produce these ratings and we are not going to pretend otherwise.
What we measure
| What | How it is measured | Why it matters |
|---|---|---|
| Bridge width | We shrink the keep area by a set width, then check whether it broke apart. We try five widths: one thirty-second, one sixteenth, three thirty-seconds, one eighth and three sixteenths of an inch. | The first width that breaks the design is the width of its weakest strip. That strip is what snaps. |
| Floating pieces | We look for any area of skin bigger than about a fiftieth of a square inch that has cut area all the way around it. | Those pieces fall out. One can be a nice touch. Many mean the design collapses. |
| Cut regions | A count of the separate holes you have to make. | This is mostly about how long it takes, not how hard it is. |
| Detail density | Inches of cut edge divided by square inches of cut area. | High numbers mean long, thin, wiggly slots. Those are slow and easy to ruin. |
| Speck cuts | A count of very small holes. | Lots of tiny holes is the signal that a design wants etching instead of cutting. |
| Cut area share | How much of the page is black, and how much of that black sits in slots under an eighth of an inch wide. | Cut away too much and there is not enough pumpkin left to hold the shape. |
How Easy, Medium and Advanced are decided
Six of the measures each score zero, one or two points. Add them up. A total of two or less is Easy. Three to six is Medium. Seven or more is Advanced. The points come from the number of cut regions, the detail density, the number of floating pieces, the width at which the bridges fail, the total length of cut edge, and the number of speck cuts.
A design is also marked cut and etch when it has a lot of speck cuts, or when more than half its cut area sits in slots under an eighth of an inch, or when its detail density is very high. Those designs print with three bars as well, because scraping fine detail is not beginner work.
The 250 designs on this site
121 Easy · 51 Medium · 78 Advanced, of which 75 are marked cut and etch.
Why a simple picture can be hard
Difficulty lives in the material you leave behind, not in the material you take away. A cat silhouette looks like one shape, but if the whiskers are hairlines then the pumpkin between them is a hairline too, and it tears. Meanwhile a grinning face with twenty fat teeth has twenty easy cuts and thick skin everywhere. That is why we measure the keep area rather than counting how busy the drawing looks.
The time we got it wrong
The first version of the bridge test measured the narrowest point of the keep area directly. It rejected 441 of the 600 designs we ran through it, nearly all of them for bridges of about two hundredths of an inch. When we looked at what it had thrown out, the pile was an owl, a rooster, a rabbit, palm trees and a skeleton. Perfectly good stencils.
The test was reading the jagged pixel edge of the artwork as if it were real thin pumpkin. We replaced it with the shrink test described above, which asks a structural question instead of a statistical one: shrink by a real width, and see whether the design survives. The reject count went from 441 to 12 out of 600, and those 12 were genuinely broken.
We are telling you this because a rating is only worth something if you know how it was produced, including the version that was wrong.
What we do not claim
- · We did not carve a test pumpkin for every design. We measured the art.
- · No panel of carvers rated these. A program did, to fixed rules.
- · Pumpkins vary. A thick-walled pumpkin forgives a thin bridge that a thin-walled one snaps. The rating is about the design, not your pumpkin.
- · Easy does not mean safe. Every rating on this site assumes an adult is doing the cutting.
Where the ratings show up
The three-bar meter appears on every design page, on every card in the catalog, in every digital pack, and printed on every page of the five paperbacks. It is the same scale in all four places, read from the same measurements.
Questions
- Do you carve a test pumpkin for every design?
- No, and we will not say we do. The rating comes from measuring the artwork itself: we turn each design into a black-and-white mask and measure the shapes. Nobody carved 600 pumpkins.
- What is a bridge?
- A bridge is a strip of pumpkin skin left between two cuts. It is what holds the piece above it in place. Thin bridges are the single most common reason a stencil falls apart while you carve it.
- What is a floating piece?
- A floating piece is a part of the design with cut area all the way around it and nothing joining it to the rest of the pumpkin. When you finish the last cut it drops out. Some designs use one deliberately, as an eye or a pupil, and that is fine. A design with a dozen of them is not.
- Why is a simple-looking design sometimes rated Advanced?
- Because difficulty is about the cutting, not the picture. A plain silhouette with one long hairline gap in it is harder to carve than a busy face made of big round shapes. The measurement looks at the width of the material you have to leave behind, which is not the same thing as how detailed the drawing looks.
- Why do some busy designs stay Easy?
- Lots of separate cuts is not the same as hard. If every cut is wide and every strip between them is thick, a design with twenty holes in it is still straightforward. It just takes longer.
- What does cut and etch mean?
- Etching means scraping the skin off without cutting all the way through. The flesh underneath glows when a light is inside. Designs marked cut and etch have detail too fine to cut cleanly, so scraping gives a better result than sawing.