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Texture · Intermediate

Thermal stitch

Thermal stitch is single crochet (UK double crochet) worked through two loops at once: the back loop of the next stitch and the loop that the row before left unworked, which lies just behind it. Every row is hooked into the row below as well as the one you are working on. The result is a dense fabric twice as thick as plain single crochet.

How to work it

  1. First row: back loops of the chain

    Work a single crochet into the back loop only of the second chain from the hook and of every chain after it. The other loop of each chain is left free. Chain 1 and turn.

  2. Find the two loops

    Tip the top edge toward you and look down on it. The next stitch has its usual two loops, front and back. Just behind the back loop lies one more strand, running the same way: on this row it is the free loop of the chain.

  3. Hook under both

    The hook passes over the front loop of the next stitch and under two strands, both in the accent color: the back loop of that stitch and, just behind it, the loop left unworked in the row below. One loop is on the hook.

    Put the hook under the back loop of the stitch and under the free loop behind it. Leave the front loop of the stitch alone. Yarn over, pull up a loop, yarn over and pull through both loops on the hook: a plain single crochet.

  4. Repeat on every row

    Work every stitch of the row the same way, chain 1 and turn. On the next row the strand behind each back loop is the front loop that the row before left unworked. Go through that and the back loop again. This is the row you repeat.

  5. Close the last row

    On the last row, put the hook under both loops of each stitch and under the free loop behind them: three strands. That leaves no loop free along the top edge.

The stitch pattern, row by row

Multiple
Chain any number of stitches plus 1 (5 or more).
Starting chain
The rows here are written for a chain of 21.
  • The ch 1 at the start of a row does not count as a stitch.
  • From row 2 on, every stitch is worked through two loops at once: the back loop of the stitch and the unworked loop of the row below, which lies just behind it.
  • On row 2 the unworked loop is the loop of the foundation chain that row 1 did not use.
  1. Foundation. Ch 21.
  2. Row 1. Sc in BLO of 2nd ch from hook and in BLO of each ch across (20 sc).
  3. Row 2. Ch 1, turn; sc in each st across, working each sc through the BLO of the st and the unworked loop of the ch below it (20 sc).
  4. Row 3. Ch 1, turn; sc in each st across, working each sc through the BLO of the st and the unworked loop of the row below (20 sc).
  5. Last row. Ch 1, turn; sc in each st across, working each sc through both loops of the st and the unworked loop of the row below (20 sc).

Repeat row 3 for the pattern, then work the last row once.

Abbreviations in these rows

ch
chain stitch
sc
single crochet (UK double crochet)
BLO
back loop only
st
stitch

At a glance

Used for
thick washcloths and dishcloths; pieces that should be dense and sturdy
In UK terms
thermal stitch, the same name: a double crochet worked through the back loop and the free loop of the row below
Strands the hook goes under
2 on every row but the last, where it is 3
Multiple
Any number of stitches. The chain is one more than the stitches.
Row repeat
Row 3.

The thickness comes from the join. A plain row stands on top of the row below. A thermal row is fastened to two rows at once, the one below it and the one below that, and that overlap is what makes the fabric double thick.

Which loop is which gets easier with the edge tipped toward you. Nearest to you is the front loop of the stitch, and it stays free. Next is the back loop. Right behind the back loop, and lying alongside it, is the loop left over from the row before. The hook takes the second and the third.

It works over any number of stitches, so it needs no multiple.

The same idea is worked with taller stitches too: there are thermal versions of half double crochet (UK half treble) and of double crochet (UK treble).

When it goes wrong

My fabric is no thicker than plain single crochet.
The hook is going under the top of the stitch only. Each stitch must also catch the free loop of the row below, the strand right behind the back loop.
I cannot find the free loop.
Tip the edge toward you. It lies alongside the back loop of the stitch, just behind it and a little lower. On row 2 it is the unused loop of the starting chain.
The top edge has a line of loose loops.
The last row was worked like the others. On the last row go under both loops of each stitch and the free loop behind them.

Left-handed

The pictures show the hook held in the right hand. For the left hand, read each picture as its mirror image.

Questions

Why is thermal stitch called double thick?
Because every stitch is worked into two rows at once: the row below and the loop left free in the row under that. The rows overlap, and the fabric comes out about twice as thick as plain single crochet.
What is the multiple for thermal stitch?
There is none. Chain one more than the number of stitches you want.
Can thermal stitch be worked in other stitches?
Yes. Half double crochet and double crochet both have thermal versions, worked through the same two loops.

Where to go next

Stitches

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