In general, a thread conditioner puts a protective layer on thread that guards against soil, moisture, damage caused by ultraviolet rays, mold, and mildew. Using a thread conditioner also helps release any static electricity in the thread, which is a main cause of tangling.
Thread Heaven is classified as a synthetic silastic polymer that has the consistency of beeswax, but is not wax-based or petroleum-based. Beeswax, whether natural or synthetic, also forms a layer between the thread and fabric, but it can leave a sticky coating on the thread that can attract dirt and hold it in place.
Thread Heaven is safe for use on textiles. It cuts down on the stress caused by thread drag—the wear caused by continually pulling a thread through the fabric while stitching—and creates a slick, protective layer between the thread and the fabric.
While Thread Heaven is one of the more widely known thread conditioners with slits in the side, making it a little easier to use, there are similar thread conditioner products available at large sewing and craft stores as well.
How to Use Thread Conditioners
It's always a good idea to check the manufacturer's instructions for use, but most work the same way.
Run the thread along the conditioner, holding the thread against it with your finger or thumb to lightly coat the thread. Next, pull the thread between your thumb and finger to smooth it and remove any static.
You might wish to repeat this to add an extra coating in some cases.
When to Use (and Not Use) Thread Conditioner
Because products like Thread Heaven protect your thread and reduce tangling as you work, you might want to start using it every time you stitch. In fact, once you try it, you might just find yourself hooked on it.
It's especially helpful when working with metallic threads, which easily become damaged as you repeatedly pull them through your fabric. It's also useful for taming satin or rayon embroidery threads or DMC's neon and glow-in-the-dark Light Effects threads.
That said, some more textured threads aren't suitable for use with thread conditioners. Additionally, some stitchers find that when using thread conditioners on white threads, the conditioner grabs onto dust and dirt, causing the thread to have a grayish cast. Use it with caution on whitework.
In addition to using thread conditioner for embroidery and cross-stitch, it's also useful for bookbinding, quilting, beading, and more.