How to Spread-Sink a Paper Corner After a Closed Sink

A closed sink turns a projecting corner inward without allowing the affected paper to open completely flat during the maneuver. Robert J. Lang explains that its distinguishing features lie in the hidden creases and distribution of layers; those layers can also form a locking arrangement. Robert J. Lang’s “Origami Diagramming Conventions”

A spread sink, also called a squash sink, has a relationship to an open sink: Lang illustrates how its spread configuration can collapse into a conventional open sink. That relationship explains the combination of inward movement and spreading, but it does not mean every completed closed sink can simply be pulled open. Lang’s explanation of sink variations

Treat “after a closed sink” as a position in your folding sequence. First establish whether the next arrow selects the same region, an adjacent corner, or a flap exposed by the previous operation.

Before touching the paper, compare three views: the drawing before the closed sink, the drawing after it, and the result of the spread sink. Use an unchanged edge or crease intersection as your reference. This gives you a way to track the working corner even when its tip becomes hidden.

Check the following details:

• Orientation: Has the model been rotated or turned over?
• Working flap: Where does the movement arrow begin?
• Layer selection: Does the arrow hook around a particular flap?
• Destination: Which edge or crease changes position in the following drawing?

Lang describes hooked arrows and schematic edge views as ways to distinguish moving layers. Read these details before assuming that every layer beneath a visible corner moves together. “Origami Diagramming Conventions”

If the paper does not resemble the starting drawing, resolve that mismatch first. A useful comparison is the location of the nearest free edge: matching the outside outline alone may leave an incorrect layer arrangement unnoticed.

Locate the crease marking the sink boundary. If the instructions include a fold-and-unfold step, complete it before attempting the collapse. General sink instructions recommend establishing the sink crease in both directions, then opening the available layers enough for the surrounding paper to reverse. Apply that advice only to the region selected by your diagram. Origami Diagrams’ sink-fold instructions

Support the model close to the working area with one hand. With the other, test the opening between the selected layers. You are looking for enough movement to guide the corner, without dismantling the preceding fold.

Abrashi Origami School’s illustrated comparison shows why this distinction matters: an open sink has layers that can separate, while a closed sink has a tightly interwoven arrangement. Resistance at that closed arrangement is a reason to recheck your working location. “What is Origami Sink fold?”

The following sequence is a practical synthesis of sink and squash mechanics. Use your model’s marked creases and next drawing to determine the exact geometry; these steps do not supply missing crease locations.

1. Lift the selected flap slightly. Keep the surrounding model supported so you can see which layers are opening.
2. Separate the working layers. Open the local pocket enough to reach or guide the corner. Leave layers that the diagram keeps together in their existing arrangement.
3. Begin the indicated flap movement. If the diagram also shows a flap swinging sideways or downward, begin that motion while the pocket remains open.
4. Guide the corner inward. Ease it along the sink boundary, allowing the adjacent paper to change its fold direction.
5. Spread the surrounding paper. Let the sides move into the shape shown in the result instead of compressing the entire corner into a narrow stack.
6. Align, then flatten as instructed. Check the new edges and crease positions before pressing firmly.

The opening and alignment actions resemble a squash fold. Origami Resource Center teaches that operation by lifting a flap, separating its layers, and pressing it down while aligning the top crease with the paper beneath. This is a useful mechanical reference, though your spread sink may have a different final shape. “Origami Squash Fold”

Work through the movement loosely once before sharpening it. If a side folds across an unmarked area, pause with the pocket partly open and compare it with the diagram again.

Use the next drawing as your completion test. Check the position of the former corner, the outline of the spread region, and which flap lies on top. Press the result fully flat only when the instructions show a flat result.

For a symmetrical configuration, compare the two sides before setting the creases. Origami.me’s squash-fold example specifically calls for symmetrical sides; its guide also notes that the same fold can appear in different shapes across models. Follow that symmetry check when your diagram calls for it. “Learn How to Make Origami: The Complete Beginner’s Guide”

Then check the preceding closed sink. Unless the sequence explicitly changes it, its tucked layers should retain their intended relationship. Abrashi distinguishes an unsink as bringing a previously sunken point outward. If that is what your paper is doing, compare the arrow and selected flap again before continuing. Abrashi’s explanation of unsinking

Use this diagnostic sequence before adding pressure. It combines the references’ crease and alignment advice with checks against your model’s drawings.

What you observe	What to check	Next action
The corner wrinkles before moving inward	Sink crease and available opening	Ease back, reinforce the specified crease, and reopen the permitted layers.
Only part of the intended corner moves	Layer selection	Compare the arrow’s starting point and any hooked layer indication.
The opened flap flattens crookedly	Alignment inside the pocket	Lift it slightly and realign the working crease before pressing.
The earlier sunk point comes outward	Whether you selected the correct region	Return to the preceding drawing and trace the working flap again.
The outside shape matches but the next flap is inaccessible	Hidden layer arrangement	Compare the exposed edges and flap order before proceeding.

Weak precreases and insufficient freedom for the layers to move are documented causes of unsuccessful sinks. Correct those conditions gradually; pressing harder does not establish the missing crease or identify the correct layer. Origami Diagrams’ sink troubleshooting

If separating and flattening the pocket remains unfamiliar, rehearse an ordinary squash fold on a separate preliminary base. Origami.me provides both the base instructions and a squash example: lift one of the base’s four flaps, then flatten it symmetrically. This isolates the opening action before you return to the more constrained corner. Origami.me’s basic-fold guide

Return to your model with three checkpoints: select the indicated layers, let the corner move while its surrounding paper spreads, and compare the loose result with the next drawing. Set the creases once those relationships match. That sequence gives you a concrete way to finish the spread sink while preserving the folds needed for the following step.

• Robert J. Lang, “Origami Diagramming Conventions”.
• Abrashi Origami School, “What is Origami Sink fold?”.
• Origami Resource Center, “Origami Squash Fold”.
• Origami.me, “Learn How to Make Origami: The Complete Beginner’s Guide”.
• Origami Diagrams, “Sink fold”.