Bobbin thread showing on top of embroidery: what it means and how to fix it

Look closely at the front of the design. You may see white or black dots along the edges of satin columns, a faint speckle across fills, or in bad cases, a line of bobbin thread running alongside the top thread. All three mean the same thing: the knot where top and bobbin threads interlock is being pulled up to the surface. That happens when the top thread pulls harder than the bobbin thread can resist.

Fix it in this order

1. Rethread the top thread with the presser foot up. A thread that is wedged badly in a guide, wrapped around a spool pin or caught on a spool notch adds drag that acts exactly like high tension.
2. Fit a new needle. A damaged eye adds friction to the top thread on every stitch. Use 75/11 for 40 wt thread.
3. Clean the bobbin case. Lint under the bobbin tension spring lifts the spring and lowers bobbin tension, which has the same effect as tightening the top. Remove the case or cover, brush the spring and slot, and blow the lint away gently (avoid canned air that drives lint deeper).
4. Check the bobbin. Is it the right type and size for your machine, inserted in the correct direction, and drawn through the tension slot? Is it embroidery bobbin thread, evenly wound?
5. Lower top tension and run an I-test. Reduce top tension in small steps. On an I-test the bobbin thread should cover roughly the middle third of the back of a satin column. See the I-test and H-test for how to stitch and read it.
6. Adjust bobbin tension only if you must. If top tension is already low and the test still shows too little bobbin on the back, the bobbin may be too loose. Our bobbin tension guide covers the drop test and small screw adjustments.

Why does the bobbin thread come to the top?

In a balanced embroidery stitch, the top thread wraps over the surface and dips down to meet the bobbin thread just under the fabric, so the back shows a stripe of bobbin thread with top thread on either side. Embroidery is deliberately set with more top thread pulled to the back than in garment sewing, which is why the back of a satin column shows about one third bobbin and two thirds top thread. When the top pull becomes stronger than the bobbin's resistance, the interlock rises through the fabric and appears on the surface. The table lists what increases the top pull or weakens the bobbin's resistance.

How to read where the bobbin shows

Along both edges of every satin column

General imbalance: top tension too high or bobbin too loose. The I-test will show it.

Only on one edge of satin columns

Often the needle or thread path rather than tension: a needle rotated or bent slightly, or the fabric shifting one way. On multi-needle machines, also check hook timing on that machine if it happens on all needles.

Scattered specks across fills

Mild imbalance plus a fill with very short stitches; can also be a light stabilizer letting the fabric pull up.

Only with one thread color or brand

That thread is thicker, slipperier or more twisted than your usual thread. Adjust top tension for that spool.

Only on the first few stitches

The bobbin thread was not pulled up and held, or the machine started at full speed.

Single-needle vs multi-needle machines

Home single-needle machines

Most home embroidery machines have one top tension dial or a tension setting in the embroidery menu, and many show a default number for embroidery. Some brands recommend a lower top tension for embroidery than for sewing. Check your manual for its suggested range rather than copying numbers between brands, since the scales differ.

Several brands, including some Brother, Baby Lock and Janome models, ship with a second bobbin case marked for embroidery or for a particular bobbin thread, set to a different tension from the standard case. Using the wrong one for the bobbin thread you have loaded is a known cause of bobbin showing on top. Check whether your machine came with an extra case and which one your manual specifies for embroidery.

Multi-needle machines

Multi-needle machines use a front-loading bobbin case with an adjustable screw and a separate tension knob for each needle. If bobbin shows on one color only, it is that needle's tension, so compare the pull of that needle with a needle that is stitching well. If it shows on all needles, check the bobbin case: commercial operators commonly use a tension gauge or a consistent drop test to set the case. Prewound bobbins from reputable makers help keep the bobbin side consistent across runs; see bobbin thread and prewound bobbins.

When the design causes it

Designs with very dense fills, multiple overlapping layers or very short satin stitches pull hard on the fabric. As the fabric gathers, the bobbin is dragged into view even when tension is correct. If bobbin thread appears only in particular objects, compare the design's stitch density with typical values (around 0.4 mm spacing for satins and fills is common), and check that it has underlay. Narrow satins also need room for the knot; see satin stitch problems.

Prevention

• Use the bobbin case and bobbin type your manual specifies for embroidery.
• Use lightweight embroidery bobbin thread consistently.
• Run an I-test when you start a new thread brand or after any tension change.
• Clean the bobbin case every few bobbins; lint builds faster than you expect.
• Write down your machine's normal embroidery tension setting so you can return to it.