Monday Masterclass

Understanding Underlay – The Hidden Foundation of Beautiful Embroidery

When we admire a beautifully stitched embroidery design, our eyes are naturally drawn to the visible stitching—the smooth satin columns, beautiful fill stitches, and decorative details that bring a design to life. Yet hidden beneath almost every professionally digitized embroidery design lies something you'll rarely notice once the embroidery is complete.

That hidden layer is called underlay.

Think of underlay as the foundation of a house. Nobody admires the concrete slab once the home is finished, but without it, the walls begin to crack and shift. Embroidery works in exactly the same way. The visible stitches provide the beauty, but the underlay provides the structure that makes everything else possible.

Once you begin recognising underlay, you'll start to understand why some embroidery designs stitch beautifully while others struggle. It also becomes much easier to identify the causes of problems such as gaps, puckering, poor coverage, or lettering that simply doesn't look crisp.

Here is a short video to illustrate some of the underlays. Click on the image below to view the Video

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Why Does Underlay Matter?

Fabric isn't a solid surface.

Every time the needle penetrates the material, the fabric stretches, compresses and moves. Without something stabilising that fabric first, the decorative stitches can sink into the material or pull the fabric out of shape.

Underlay performs several important jobs before the visible embroidery even begins.

It helps to:

• Stabilise the fabric before the decorative stitches are sewn.
• Hold down the nap or pile on textured fabrics such as towels and fleece.
• Support satin stitches so they remain smooth and slightly raised.
• Prevent gaps caused by the fabric moving during stitching.
• Reduce puckering by spreading stitch stress across a larger area.

Although you'll rarely notice underlay in the finished embroidery, you'll certainly notice when it isn't there.

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The Five Main Types of Underlay

Professional embroidery software includes several different underlay types. Each one has a specific purpose, and experienced digitizers often combine two or more underlays to achieve the best possible results.

Let's look at each one from a stitcher's point of view.

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1. Centre Run Underlay ---------

Imagine drawing a single straight line down the centre of a satin column.

That is essentially what a Centre Run Underlay does.

It creates a backbone for the satin stitches that will follow.

While it doesn't provide a great deal of fabric support on its own, it gives narrow satin columns something to anchor themselves to, making small lettering and delicate details much more stable.

You'll often find Centre Run under:

• Small lettering
• Narrow satin borders
• Thin stems
• Delicate decorative elements

Think of it as the reinforcing steel hidden inside concrete.

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2. Edge Run Underlay ======

Instead of stitching through the middle, Edge Run Underlay follows both edges of a satin column.

Rather than supporting the centre, it supports the outline.

This helps create crisp, clean edges while preventing satin stitches from pulling inward during embroidery.

Edge Run is particularly useful whenever sharp, well-defined edges are important.

Often used beneath:

• Medium to large satin columns
• Satin borders
• Appliqué edges
• Shapes requiring crisp outlines

If you've ever admired embroidery with beautifully clean satin edges, Edge Run probably played an important role.

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3. Zigzag Underlay xxxxxxxx

This is probably the easiest underlay to recognise if you've ever watched a design stitch.

Before the satin stitches begin, you'll often see wider zigzag stitches travelling back and forth across the area.

Their purpose is simple—they lift and support the satin stitches that follow.

Instead of allowing the decorative stitching to sink into the fabric, the zigzag creates a soft platform underneath.

This is especially valuable on fabrics with texture, thickness or pile.

Common uses include:

• Large satin lettering
• Monograms
• Wide satin borders
• Decorative satin elements

If satin embroidery appears slightly raised and luxurious, Zigzag Underlay is often the reason why.

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4. Tatami Underlay =======

Tatami Underlay resembles a light fill stitch.

Rather than supporting satin stitching, it is designed to support fill (tatami) embroidery.

Large filled areas place considerable stress on fabric. A light layer of underlay helps spread that stress more evenly before the decorative fill begins.

The result is better coverage, improved stability and less distortion.

You'll commonly find Tatami Underlay beneath:

• Large filled flowers
• Animals
• Filled backgrounds
• Decorative filled motifs

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5. Double Tatami Underlay HHHHH

Sometimes one layer simply isn't enough.

For particularly large filled areas or difficult fabrics, digitizers may use two Tatami Underlay layers, each stitched in a different direction.

The crossing stitch angles create an even stronger foundation.

Think of it like laying two sheets of plywood at opposing angles to strengthen a floor.

Double Tatami Underlay is especially useful for:

• Very large filled designs
• Soft or stretchy fabrics
• Designs requiring excellent coverage
• Projects where maximum stability is needed

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Combining Underlays

One of the biggest misconceptions is that an embroidery design only uses one type of underlay.

In reality, professional digitizers often combine several underlay types because each one performs a different job.

Centre Run + Zigzag

The Centre Run creates the backbone.

The Zigzag creates the platform.

The satin stitches are then sewn over both, producing smooth, raised and stable embroidery.

This combination is extremely common in quality satin lettering.

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Edge Run + Zigzag

The Edge Run keeps the edges crisp.

The Zigzag provides height and support.

Together they create satin columns that appear clean, full and professional.

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Tatami + Additional Tatami

Large filled areas sometimes benefit from two supporting Tatami layers to improve stability and reduce distortion on challenging fabrics.

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What Can You Learn as a Stitcher?

Even though you may never digitize your own embroidery, understanding underlay can make you a much better embroiderer.

The next time your machine begins stitching a design, don't immediately focus on the decorative stitches.

Instead, watch what happens first.

Ask yourself:

• Is there a single line stitched down the centre?
• Are stitches following the outside edges?
• Is a zigzag pattern being sewn first?
• Is there a light fill underneath before the main fill begins?

Recognising these clues helps explain why one design stitches beautifully while another may struggle on the very same fabric.

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Can There Be Too Much Underlay?

Interestingly, yes.

While too little underlay creates weak embroidery, too much underlay can create unnecessary stitch density.

This may result in:

• Stiff embroidery
• Longer stitch times
• Increased thread breaks
• Excessive bulk

Good digitizing is always about balance.

The goal isn't to use more underlay.

The goal is to use the right underlay for the fabric, stitch type and design.

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Final Thoughts

Underlay may never be the star of the show, but it quietly determines how successful your embroidery will be.

The next time your machine begins stitching a design, don't rush to admire the decorative thread just yet. Watch those very first stitches carefully—they're revealing the hidden engineering inside the design.

Once you learn to recognise Centre Run, Edge Run, Zigzag, Tatami and Double Tatami underlays, you'll begin to understand why quality embroidery looks the way it does. More importantly, you'll become much better at recognising well-digitized designs and identifying the causes of stitching problems.

After all…

The most beautiful embroidery isn't built from the top down.

It's built from the foundation up.