HomeDec Tech: Linings and Interlinings Part II

In Part I of this topic I shared a little about sateen lining, the basic go-to lining for window treatments.  (See HomeDec Tech: 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 a 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 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 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?

FBO11     FBO12

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.


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.


Not everyone wants to block sunlight, and having light filter through fabric is a beautiful thing.  We 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.  Apollo is 100% polyester, and is woven with black fibers sandwiched in the middle.  (It does not have foam applied to the fabric).  It is a soft, fluid material that doesn’t wrinkle so it is a great choice for many styles of window treatments, but it will not hold folds or creases and does not marry well with face fabrics.  This can cause separation of the layers, and billowing.  Not a problem on a puddled drapery, or stationary balloon shade but it is a problem on a traversing drapery, or functional shade.


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 hem.  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.

Stay tuned for more HomeDec Tech lining lessons coming soon.  If you have any questions I am happy to help!

Best Wishes,

Susan AKA Home Dec Gal


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  1. Ruth Zahler at Jan 03, 2014 04:44:39

    Very good information on linings for custom draperies. Thank you.

  2. Kathy at Dec 20, 2014 04:18:22

    Do you use another interlining with blackout or is it sufficient Thanks Kathy Buzbee

  3. Susan Woodcock at Jan 04, 2015 01:18:03

    Hello Kathy,
    If you want the added layer of flannel interlining for insulation or to add body to a thin fabric then it’s fine to add it with blackout, but blackout is sufficient on it’s own as well.
    Best Wishes,

  4. Susan Woodcock at Feb 12, 2015 04:29:14

    Hello Kathy,
    Yes, you can use interlining with blackout lining. It’s heavy but sometimes you need the softness of flannel even with blackout.
    The better quality blackout linings are not difficult to sew but there can be pinholes of light at seams. I usually serge together pieces of blackout. Some workrooms use adhesive tapes to join blackout. I do prefer to hand stitch the side hems.
    I hope this helps. Thanks for reading my blog and for your question.
    Susan, HomeDecGal

  5. Gwen Hamiltton at Jun 05, 2015 04:07:04

    Could you clarify what you mean by serging pieces of lining together? Thanks

  6. Susan Woodcock at Jun 05, 2015 04:19:04

    Hello Gwen,
    I am referring to sewing with a serger or overlock machine to join the pieces of lining together. A serger cuts and finishes all at the same time so it’s very efficient and makes a really clean, secure seam. Please let me know if you have any other questions and thanks for visiting my website!
    Best Wishes,

  7. Julie at Nov 13, 2015 12:21:36

    Great post! I do find the light going through the stitches disappointing!

  8. Lib at Feb 15, 2016 01:53:37

    I have used blackout lining with standard interlining for valances with pleats and they hang beautifully. The main fabric can be any weight. My lining choice is made because I want the valance to look the same color during the day as most clients choose to span from ceiling to some point below window frame. I believe it looks odd when a valance is hung this way and the lower portion looks see-through during daylight. I always interline unless the client orders upholstery fabric to match their furniture. Blackout really protects expensive fabric.

  9. Susan Dunn at Jun 04, 2016 10:09:46

    This is very helpful. Is there any way of avoiding the pinholes? Thanks.

  10. Susan Woodcock at Jun 04, 2016 02:54:18

    To help eliminate pinholes of light on blackout draperies, I recommend hand sewing the side hems. You can also use adhesive iron-on tapes. For Roman shades I have a couple of innovative teahniques that I have developed for my own clients which I have shared on my YouTube channel and you can watch to learn how this is accomplished.
    Best Wishes,
    Susan AKA HomeDecGal

  11. Lisa at Oct 06, 2016 05:40:18

    I have some drapery panels that are made out of a cream linen. I used blackout lining and now have black coming through in the pinhole/ stitch. Does anyone have a solution for this? Please help!

  12. Susan Woodcock at Nov 17, 2016 10:59:40

    I am sorry you have this issue with the blackout lining. Once the lining is pierced with the needle like that, you can’t repair it. If the stitching is along a side hem, youu might be able to take out the stitching and brush the fabric and then hand stitch it instead of machine sewing. If it’s where the pleats were sewn, I can only suggest trying a spot or stain remover and then brushing the fabric to loosen the fibers to hide the black spots. I hope you can get this fixed.
    Good Luck,
    Susan AKA HomeDecGal

  13. Cristina at Feb 13, 2017 07:36:15

    Hi! I just found your site. I’m in the middle of making several roman shades for my house, and one room needs blackout lining. The other shades I made with cotton lining came out great, but the blackout lining is causing a little bit of trouble. I’ve been using iron-on rib tape, but from what I understand, I can’t use a hot iron on the blackout fabric. Is that right? I tried to iron on hot with a cotton pressing cloth, and it seemed to adhere fine without too much puckering, but today the rib tape just pulled right off. I’m using fiberglass ribs, so I wonder if I’m better of using the rib support rings for my lift cord and ditching the iron-on rib tape. Or is there a blackout fabric that I can use iron-on tape with? Thanks!

  14. Susan Woodcock at Feb 13, 2017 08:29:21

    Hello Christina,
    I am sorry you are having trouble with adding ribs to blackout. There are a couple of options. One is to actually glue the ribs to the blackout lining, on the wrong side. You can see more about that by visiting The Workroom Channel’s youtube channel and looking at the videos with Elki Horn. Another method is to sew rib pockets in the lining fabric but with blackout you could still see pinholes of light so I prefer to add a layer of interlining with the rib pockets sewn in the interlining. Add the ribs before you finish with the blackout lining. This is shown in my book Sewing Custom Curtains, Shades and Top Treatments or you can view a how-to on the Home Dec Gal Youtube channel.
    I hope this helps!
    Good luck,
    AKA Home Dec Gal

  15. Cristina at Feb 21, 2017 02:52:10

    Thank you so much! I ended up doing a French blackout, but only needed two layers because my face fabric is very dark. It worked perfectly! Though I would like to try putting the ribs inside at some point. Maybe the next room!

  16. Susan Woodcock at Feb 22, 2017 05:33:30

    That’s great! I love it when the fabrics work with us and not against us. :)
    Thank you for following up.

  17. Janine Moreno at Sep 14, 2017 09:02:09

    Hi! How can avoid the bulky lining, I sew the header (lining and fabric) and when I do the side hems and sew the buckram, I get bulky lining, can you give me an advice. Thank you!!

  18. susanlw62 at Oct 11, 2017 06:39:58

    You might want to change your fabrication techniques for making draperies. Have you ever tried a “low bulk heading”? You can find this and the double fold heading method for draperies in my book “Sewing Custom Curtains, Shades and Top Treatments”.
    Best Wishes,

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