My method for joining new yarn is super simple. You simply knit about 15 stitches with doubled yarn. In other words, you hold the new yarn and the old yarn together and knit them at the same time. 

On the next row, you can knit the double stitches together as one and cut off the loose ends.  

This method is super simple, quick, and nearly invisible. At the same time, the join is completely secure and cannot come undone.

I'll explain exactly what you need to do, step by step. Here you'll learn a super-simple method that will stay with you forever—no more frustration when changing yarn!

The classic method for joining a new ball of yarn is usually a simple knot.

For these reasons, I don't think knotting the yarns together when changing yarn is a good idea:

• A knot can come undone, causing a hole
• Knots can be noticeable to the touch
• Knots can create unsightly bulges
• Knots can shift to the right side of the knitted piece and become visible

For these reasons, I avoid knots. If I come across a production-related knot within a ball of yarn, I usually undo it and use my double-knitting method as well.

Step 1: 

Let the existing strand run out for about 30 cm. Make sure the end isn’t too short, so you can comfortably knit about 15 stitches with it.

Step 2: 

Add the new strand. Make sure to overlap the beginning of the strand securely. Place the new strand alongside the old one and hold both together in your left hand.

Step 3: 

Work about 15 stitches with both strands held together. To do this, knit the new and old strands simultaneously as if they were a single strand—in other words, double-stranded. 

Step 4: 

Knit the new stitches once on the next row or round. To do this, knit each double stitch as one stitch.

Step 5: 

You can now simply cut off the excess ends. Be careful not to cut too close; I usually leave about one centimetre so that I don’t accidentally damage the existing stitches.

I use my double-knitting method with almost all yarns. It is especially well suited to very thin and fine yarns, as the join is so smooth. 

I have also used the double-knitting method with very thick yarns. In this case, a slight thickening is visible in the double-knitted area, but it is hardly noticeable.

When changing balls of yarn in solid-colour knitted pieces, I always use the double-knitting method. 

The only exception for me is colourwork projects when changing colours. Since the change must take place at exactly the right point, tying a knot is unavoidable. It works well to make a slipknot around the main yarn. Since both yarns continue to be worked, this knot does not cause any problems with gaps.