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  • Writer's pictureSusan Woodcock

Linings and Interlinings: Part II

Updated: Oct 31, 2022

In Part I of this topic I talked about sateen lining, the basic go-to lining for window treatments. See Linings and Interlinings Part I. The next most popular linings are "dimout" and "blackout", which are valued for their insulation and light blocking capabilities.

Most light blocking linings (blackout and dimout) have an acrylic foam product sprayed on one side of a cotton, polyester/cotton blend, or polyester substrate (or base cloth). The number of times the coating is applied is referred to as "passes". The more passes, the more light that is blocked so a dimout lining is known as a 1-pass material, and a blackout is a 3-pass. The foam layer also helps improve insulation against heat and cold on window treatments that close completely like traversing draperies. Premium quality dimout and blackout linings may cost a little more, but they have a softer hand and are easier to sew. Lesser quality materials can feel rubbery, and are difficult to feed through the machine.

How do they compare

In the photos below you can see the difference between a dimout lining and a blackout lining combined with silk fabric. Dimout (AKA Thermal Suede) does help to block damaging sunlight, but to completely block light a blackout lining is the best option. Keep in mind that side hems, facings and other areas where the face fabric wraps to the reverse side will not be protected from sunlight.

blackout lining
blackout lining

Blackout is the perfect lining for fabrics that are embroidered, or woven with floating threads on the reverse side; like the fabric below. Can you imagine how this would look at the window if it was lined with a sateen, or dimout?

light shining through embroidered fabric

Blackout sounds like the perfect lining, doesn't it? It is a great product in many ways, but one of the drawbacks of blackout lining is that when a needle pierces the foam layer, it leaves a hole. In the photos below I have machine sewn a hem, and hand stitched a shade ring. As you can see, this creates tiny pinholes of light. Why is this a problem? It may look like a tiny spot of light here, but on a large window treatment with lots of stitching it can be very annoying! This is especially true on Roman shades, where rings or shroud tapes are stitched up and down the back of the shade.

stitched pinholes of light
pinholes of light with hand stitching

There are solutions to prevent or conceal light holes. I have seen suggestions to paint over the holes with a product sold by lining companies, or even gesso or white out. While this does work, I am skeptical about how this will last long term as window treatments are used daily and exposed to sunlight, changes in temperature and moisture. There are fabrication methods that can minimize the amount of stitching needed, such as using adhesive tapes at hems and headings, and iron-on rib tape on the back of Roman shades. Hand sewing side hems can also leave less noticeable holes than using a blind hemming machine.

In the video below I show my method for sewing drapery side hems with blackout lining.

Not everyone wants their window coverings to block sunlight, and having light filter through fabric can be a beautiful thing. I often walk into homes and remark about how bright and sunny they are! But for media rooms, bedrooms and in homes with intense sun exposure, blackout is phenomenal.

Blackout can also be used as an interlining on window treatments that have a color lining, to keep the contrasting fabric from shadowing through to the face. An example would be swags and jabots where the lining turns to the face as the jabot is folded.

Another material to consider is Apollo (Hanes Fabrics) which is a woven material that filters almost all light. It is a super-dimout, which will create blackout when paired with many face fabrics but will not create full blackout on light color face fabrics. Apollo is 100% polyester, and is woven with black fibers sandwiched in the middle. (See photo below). It is a soft, fluid material that doesn't wrinkle which makes it a good choice for many styles of window treatments. But, this type of material it will not hold folds or creases, and does not marry well with face fabrics. This can cause a separation of the layers, and billowing. I do not recommend this lining for traversing draperies or flat roman shades where you want the vertical or horizontal folds to remain straight and even. Apollo works better for a decorative styles of drapery with tie-backs or Italian stringing or for a drapery with added length to "break" or puddle on the floor.

There is one more blackout option; French blackout, which I will share in Part III of this series followed by interlinings in part IV.


How can you tell the which is the right side of blackout and dimout linings?

Blackout and dimout linings have a fabric side, and a coated side that feels like suede. I prefer to have the fabric side as the "right" side, but some other workrooms and designers prefer the look of the coated side. The side you use will not affect the performance of the lining, so pick a side and stick with it!

Blackout doesn't fray, do I still need to fold a double hem in the bottom?

That is correct, one of the great things about these linings is that you can get a clean cut, without any fraying. I would not leave a cut edge in custom work, and prefer to fold in a double hem, serge the edge and fold in a single hem, or in some cases serge the edge and let that be the finish. An example of when a serged edge is appropriate is when the window or door glass goes all the way to the floor, and you will have sunlight shining through the hemmed area. By not stitching a hem, you prevent pinholes of light along the bottom.

Is it okay to add blackout lining to the draperies but not the valance?

For valance styles with a soft, draped design blackout could make it bulky. If any light will shine through the valance, it should be blackout lined to match the draperies so that the colors match. Many window treatments are installed up high over the window. One solution would be to add blackout to the main valance and not to any parts that will be attached over the valance like horns or swags, as long as the under-valance will block the light.

What is the point of using a dimout if it doesn't block light? Why not just use a sateen lining?

Dimout has great insulating qualities, and does block more light than a sateen lining alone. The best idea is to compare the two linings side-by-side, using a light test like is shown here.

To see part three of this series, click here: Linings and Interlinings: Part III If you have any questions I am happy to help!

Best Wishes,

Susan AKA Home Dec Gal

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