How to Calibrate HueForge Filaments by Eye

I wasted four rolls of filament before I realized I needed to test and use my own TD values for my Hueforge prints.

That's not me selling the eyeball method as some hidden trick. It's me admitting I overthought this for months. I realized the Seashell test PDF that ships with HueForge does the same job — for free — in about ten minutes per filament. Once you've calibrated three filaments, you'll never look at the preview the same way again.

If you're a few prints in and your colors don't match the preview, this fixes it.

Before you start

This tutorial assumes:

— HueForge installed (any 0.9.x version)

— A printer that can do color swaps (manually or AMS — both work)

— Three filaments to calibrate. I recommend a black, a white you've been struggling with, and one mid-tone color you use a lot

— The Seashell reference PDF (in HueForge: Help → Print Test → Seashell), printed on plain paper

— About 10 minutes of print time per filament + 5 minutes of comparison

You don't need a TD meter. You don't need the BQ TD1S. You don't need a custom-printed calibration disc. You need the Step Test STL that comes with HueForge, the Seashell reference, and even daylight.

What TD actually is

Transmission distance — TD — is the thickness of solid filament, measured in millimeters, through which light can still penetrate before getting fully blocked.

Low-TD filaments block light fast. Black PLA almost always sits near TD 0.5 — half a millimeter of black is enough to stop nearly all light. That's why black is the universal HueForge base layer.

High-TD filaments let light pass through several millimeters of solid plastic. Some translucent whites measure TD 8 or higher. That's how HueForge stacks colors — translucent layers on top let the colors below show through, the same way watercolor washes let the paper show through underneath.

The HueForge preview is calibrated against TD values. If your Filament TD values are different than the ones listed in Hueforge, the preview lies. Your print won't match what you saw on screen — and that's the gap most beginners can't explain.

The procedure

Step 1 — Print the Step Test in your test filament over a black base

Open HueForge. File → Open and load Step_Test_Square.stl from the Tools folder inside your HueForge install directory.

Slice with the standard HueForge slicer settings:

— Layer height: 0.08mm

— First layer: 0.16mm

— Infill: 100%

— Walls: 2

Add a single color change command at layer height 0.56mm. In Bambu Studio: right-click the Preview layer slider at 0.56mm → Add color change. In PrusaSlicer: layer slider → Add Color Change at 0.56mm (this inserts an M600 G-code command). In Orca: same right-click pattern as Bambu Studio.

The first 0.56mm prints in black (the base). Everything above prints in the test filament. The print finishes at about 1.5mm tall — eight stepped sections, each a different thickness of test filament over the black base.

Print time: roughly 10 minutes on most printers.

Step 2 — Print the Seashell reference (one time, lasts forever)

In HueForge: Help → Print Test → Seashell. Save the PDF. Print it on plain white paper at full size. Tape it to a workbench surface where natural daylight hits it evenly.

This is your reference target. You won't need to reprint it unless it gets damaged.

Step 3 — Compare the printed Step Test to the Seashell

Hold your physical Step Test directly against the printed Seashell. Use even daylight from a window — not a phone flashlight, not overhead bulbs, not your printer's chamber LEDs. Daylight is the calibration standard. Anything more directional misleads.

The Step Test has eight stepped sections. The Seashell PDF has matching reference steps. Your job: find the step on your test print where the black base starts to disappear — the moment where the test filament becomes thick enough to block the underlying black.

Step 4 — Read the TD value off the reference

Each step on the Seashell is labeled with a TD value. The step where your filament's black base disappears is your filament's calibrated TD. Write it down — you'll enter it in HueForge next.

Step 5 — Enter the TD into HueForge's filament library

Open HueForge → Filaments panel. If your filament is already in the library: click it, edit TD, save. If it is a custom filament: Add Filament, name it descriptively (e.g. Polymaker PolyTerra Cotton White — calibrated 2026-05), enter the TD, save.

That's it. Repeat for filaments two and three.

Or — and this is the time-saver — batch all three Step Tests on the same plate and print them in one go. Three filaments calibrated in twenty minutes total of print time, all on one black base.

A worked example

Last month I batched three filaments on the same plate: a translucent white I had been struggling with for months, a basic black for the base, and a semi-translucent yellow I had never measured.

The black sat at TD 0.5 — that is the base layer for nearly every HueForge print I do. Black is almost always near 0.5, which is why it is the standard reference.

The white came in at TD 4.5. That is a medium-translucent white — not the most translucent on the market, but not opaque either. The HueForge preview had been showing colors washing out, which made sense once I saw the value: I had been treating it as TD 1.5 from a previous spool, but the new spool was actually three times more translucent.

The yellow landed at TD 2.5 — pretty typical for a saturated PLA color. Bright pigments in the filament block light faster than translucent whites do.

Took 22 minutes of print time and about 8 minutes of comparison. After that, my next print matched the preview the first time. For the first time in months.

Common pitfalls

If your test square has visible bands or doesn't transition smoothly between steps, your layer height is wrong. Calibration only works at 0.08mm layers. Higher layer heights muddle the steps and the comparison fails. Drop to 0.08 and reprint.

If two filaments look identical against the Seashell, you have a lighting problem. Window daylight is the calibration standard — phone flashlights mislead by being too directional, and overhead bulbs throw color casts that confuse white balance. Take both prints to a window. If they still look identical there, they probably are — some filament colors really do measure within 0.5 TD of each other.

If your TD value produces a HueForge preview that still doesn't match your actual prints, your filament has changed batch. Light-colored filaments (whites, pastels, silks) vary noticeably between manufacturing runs. Recalibrate every new spool of light filament. For dark and saturated colors, the variance is usually small enough to ignore.

The eye is enough — until it isn't

TD calibration isn't precision metrology. It's vibe metrology. Your eye is the instrument, the Seashell is the calibration target, and the daylight from your window is the standard light source. Once you've done it three times, you'll be calibrating new filaments in under five minutes a piece.

The TD1S meter is faster. It's also $80 you don't need to spend until you're calibrating a dozen filaments a month. For your first dozen filaments? The eyeball method is the right tool. Save the meter money for filament.

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The hardware-assisted approach is on the channel: my walkthrough of the BQ TD1S meter — same workflow at the end, different instrument up front.

And if you want a curated reference for HueForge-tested filaments to pull from, the Filament Index lives over on the website — every filament logged with measured TD ranges and what it is good for, 3dprintsbyvic.com/filaments