How to Measure Pulp for Consistent Sheets with a Pour-In Deckle Box

A pour-in handmould receives pulp directly inside a tall deckle while sitting in a water-filled pan. Arnold Grummer’s How to Make Paper describes this arrangement and distinguishes it from dipping a shallow deckle into a vat of pulp. Follow your equipment’s instructions for assembly and water depth.

Keep three measurements separate:

• Dry fiber dose: the amount of papermaking material assigned to one sheet.
• Slurry volume: the amount of fiber-and-water mixture you pour.
• Finished grammage: the dried sheet’s mass divided by its area, expressed in grams per square meter, or GSM.

Slurry volume becomes a useful dose measurement only when its fiber concentration is known and uniform. A cup of water-rich slurry and a cup containing concentrated fiber are different recipes. Weighing a squeezed handful of wet pulp also leaves the water contribution unknown.

For an initial calibration, use one material and omit decorative additions. Record the dry starting mass as a practical recipe measurement; do not describe it as a laboratory moisture-free fiber measurement. Magnolia Editions’ Magnolia PaperWeight documentation supports calculating fiber requirements from sheet dimensions and target grammage.

Choose a target sheet size and grammage. If you simply want to repeat a sheet you already like, its finished dry mass can serve as your starting target for another sheet of the same dimensions.

For a rectangular sheet, use:

Area in m² = width in cm × height in cm ÷ 10,000

Target sheet mass in grams = area in m² × target GSM

Magnolia Editions explains the corresponding mass-to-area calculation in Magnolia PaperWeight.

Here is an illustrative calculation, not a universal pulp recipe. For a 20 × 25 cm sheet at 120 GSM:

• Area = 20 × 25 ÷ 10,000 = 0.05 m².
• Target finished mass = 0.05 × 120 = 6 g.
• Use 6 g of dry starting material per sheet as the first trial dose.

Measure the deckle’s actual sheet-forming opening for your initial estimate. After drying, measure the resulting sheet if exact GSM matters. Calculate its actual grammage from its finished dimensions rather than assuming those dimensions equal the opening.

Treat the calculated dose as a starting point. Magnolia’s worked pouring example emphasizes transferring the entire furnish and notes that humidity affects finished mass. Check your trial sheets under comparable conditions before changing the recipe. Magnolia PaperWeight

The following decision aid is a practical application of the dry-fiber approach. Choose the method that makes it easiest to account for all the material entering each sheet.

Your situation	Suggested method	Main control
A few sheets and dry material available	Prepare each sheet’s dose separately	Transfer the whole portion
Several sheets from one prepared batch	Measure slurry at a known concentration	Remix before every portion
Already-wet pulp of unknown concentration	Calibrate a measured pour against dried sheets	Keep that batch unchanged

For separate doses, tare a container on a gram scale, weigh one sheet’s dry material, and prepare that portion using a consistent pulping procedure. Transfer the whole portion into the deckle. Rinse fibers remaining in the preparation container into the same pour.

For batch measuring, prepare all the material together and establish a measured final slurry volume after pulping and transfer. Adding a stated volume of water to dry material does not, by itself, establish that same final slurry volume.

Keep a ruler, gram scale, graduated jug, mixing container, and notebook beside the usual deckle-box equipment. Choose a scale whose resolution can distinguish the differences you intend to track; a display rounded to whole grams offers little detail when comparing sheets weighing only a few grams.

Use this concentration calculation:

Concentration in g/L = dry starting mass in grams ÷ final slurry volume in liters

Pour volume in liters = desired dry dose in grams ÷ concentration in g/L

Continuing the illustrative example, suppose you prepare 30 g of dry material and bring the final slurry volume to 3 L. The nominal concentration is 10 g/L. A 6 g dose therefore requires 0.6 L, or 600 mL, of uniformly mixed slurry.

That batch contains five theoretical 6 g portions before transfer losses. Do not force the final portion to the measuring line with extra water if part of the intended pulp remains elsewhere. Account for the remaining material or reserve it for a separate trial.

Before each measurement, mix through the container’s full depth, then promptly take the portion. Hand Papermaking’s Sheet Formation and Uniformity explains why agitation matters for distributing fibers and how fiber clumps produce uneven formation. Applying that principle to a measuring container helps make successive portions more representative.

Keep rinse water separate from your concentration calculation. Once you have measured a dose into a transfer jug, use a repeatable small rinse to move its remaining fibers into the deckle. If you add water to the main stock container, update its concentration before measuring another dose.

Use the same sequence for your calibration sheets:

1. Assemble the mould and deckle according to its instructions and place it level in the pan.
2. Restore the pan to the same water level before each trial.
3. Remix the stock and measure the chosen dose.
4. Pour across the sheet-forming area and transfer the remaining fibers from the jug.
5. Distribute the fibers while they are still suspended, then lift level and drain consistently.
6. Couch, press, and dry each trial using the same procedure.

Equal fiber doses still need even distribution across the mould. Hand Papermaking describes short movements in both directions to disperse clumps during drainage and explains that further shaking cannot improve formation once the surface’s free water has disappeared. Use that timing principle when forming your pour-in sheets. Sheet Formation and Uniformity

For the first trial, prioritize a repeatable pour and level lift. Avoid changing the dose, mixing routine, and drying method together; otherwise, the result will not tell you which adjustment helped.

Make three trial sheets at the same dose. Let them dry fully and weigh them under comparable room conditions. Record their individual masses and dimensions, then inspect their formation with light behind them. Transmitted light reveals uneven fiber distribution, as described in Sheet Formation and Uniformity.

Use this practical diagnostic sequence:

• Similar masses, all below your target: check complete transfer, then trial a larger dose.
• Similar masses, all above your target: trial a smaller dose.
• Widely varying masses: repeat the mixing and measuring procedure before changing the nominal dose.
• Similar masses with patchy formation: concentrate on distribution and drainage technique.

For an illustrative adjustment, suppose a 600 mL pour produces an average finished mass of 5.4 g, and your target is 6 g. Assuming the same pulp, transfer behavior, and forming procedure:

Next trial volume = 600 × 6 ÷ 5.4 ≈ 667 mL

This proportional adjustment is an estimate for the next trial. Make another small set and check it. If you started with wet pulp of unknown concentration, the same approach can establish a useful batch-specific recipe without claiming a known dry-fiber concentration.

Keep a compact recipe containing the material, dry starting mass if known, final stock volume, deckle opening, measured pour, mixing routine, and pressing and drying method. Add each trial’s finished mass and dimensions. Label unknown quantities explicitly rather than filling them with estimates.

Recalibrate when you change the material or preparation process. Keep a successful sheet beside its recipe so you can compare both its measured weight and its appearance. Your repeatable result comes from a measured dose, complete transfer, and a forming routine you can reproduce—then a finished-sheet check that shows whether the recipe needs adjustment.

• Arnold Grummer’s Paper Making — How to Make Paper
• Magnolia Editions — Magnolia PaperWeight
• Hand Papermaking — Sheet Formation and Uniformity