When selecting curtains to block out sunlight, there are a few key factors to consider: the fabric, color, and lining used. The right combination of these elements can create an effective light-blocking curtain.
Fabric Density
One of the most important factors in choosing sun-blocking curtains is the density or tightness of the fabric weave. Fabrics like canvas, brocade, velvet, wool, and faux silk typically have a tighter weave and will be more effective at blocking light than looser woven fabrics like cotton, linen, or voile.
The density of the fabric weave determines how much light can filter through the gaps between the threads. Tighter weaves leave less open space between the threads for light to penetrate. The best curtains for blocking sunlight will be made from tightly woven, opaque fabrics.
Fabrics like canvas, velvet, brocade and faux silk are composed of tightly packed fibers that create a dense, non-sheer material. Canvas is made from thick cotton or linen fibers woven in a simple over-under pattern. Velvet has a plush pile that absorbs light. Brocade uses a complex interweaving of fibers to create intricate patterns and minimize open space. Faux silk mimics the tight weave and light obscuring qualities of real silk.
On the other hand, fabrics like cotton, voile and linen have a looser open weave that allows more light to pass through the gaps in the threads. While these fabrics can work for softening sunlight, they are less ideal for completely darkening a room.
Fabric Color
Along with fabric density, darker colored curtains can absorb more light than lighter colored fabrics. Deep, saturated colors like black, dark red, navy blue, forest green and chocolate brown work best for light blocking. Lighter sheer colors like white, tan, light yellow and pastels allow more light to pass through and reflect off the fabric.
Darker fabrics absorb a higher percentage of light waves striking them, reducing glare and lowering the amount of light that bounces off the curtains into the room. Blackout curtains in dark hues can make a room feel like it is nighttime even during the day.
Lining Material
Curtains specifically designed for blackout purposes typically have light-blocking linings on the back side of the fabric. Common blackout lining materials include vinyl, felt, fleece, velvet, wool, polyester and acrylic.
These thick, opaque backing materials prevent light from filtering through the curtain fabric. Blackout linings also provide an added layer of insulation that can keep a room cooler in summer.
The thickness of the lining is measured in gauges, with higher gauges indicating a thicker, more light obscuring liner. Blackout curtain linings typically range from 6-15 gauge thickness. For maximum sunlight blocking, look for curtains with at least an 8-10 gauge liner.
Curtain Styles for Blocking Light
The style and construction of the curtains can also influence their effectiveness at controlling light.
- Tab top curtains – Tab tops have strips of fabric or ribbon sewn into the top hem to slide over curtain rods. The tabs allow the curtains to hang close to the rod for a tight closure.
- Pencil pleat curtains – Pencil pleating creates small, evenly spaced folds for a rippled effect. The pleats allow the panels to cover more window area for improved light blocking.
- Ripplefold curtains – Similar to pencil pleats, ripplefold curtains have tightly gathered pleats that expand over the rod for full light blocking coverage.
- Rod pocket curtains – Curtains with built-in pockets or casings conceal the entire curtain rod to prevent light gaps. Deeper rod pockets provide more overlap.
- Grommet curtains – Grommets with overlapped openings allow the panels to glide across the rod without light gaps between curtains.
Curtain headers like rod pockets, tab tops, ripplefolds and pleats help the curtains stack tightly against the window when closed. This prevents light from peeking through gaps along the edges or in the middle.
Inter-lining
Some blackout curtains feature triple-weave construction with an additional light-blocking inter-lining between the front and back layers of fabric. The inter-lining acts as another barrier against light infiltration.
Curtains with dense inter-lining tend to be very effective at blocking unwanted light. However, the extra layer of fabric can also make them quite heavy.
Curtain Length and Overlap
For full light blocking, curtains should be hung so they extend well past the window frame. Extra length allows the curtains to overlap in the middle and fully cover the sides without light gaps.
A good rule of thumb is to choose curtains that are 2 to 2 1/2 times the height of your windows. This provides sufficient overlap for full coverage. The added length also allows the bottom hems to puddle onto the floor rather than hanging open with light gaps.
You can further reduce light infiltration by using dual curtain rods. Mount two curtain rods above the window with a gap between them. Hang light blocking curtain panels on both rods to create a layered effect for superior light absorption.
Side, Top and Bottom Gaps
No matter how thick or well-made the curtains are, light can still sneak in through gaps around the edges. Some steps to minimize these annoying light leaks include:
- Using wide curtain overlap on standard rods or dual rods to prevent side gap light infiltration.
- Hanging rod pocket curtains or tab tops flush with the top of the window trim to block top gap light.
- Weighing down bottom hems with flat curtain weights or magnets so they hang straight and eliminate bottom light gaps.
- Installing a curtain valence over the top of the window to block top light gaps.
- Using blackout side track curtains or light blocking window shades in addition to curtains.
Best Fabrics for Blocking Light
Here is an overview of some of the top curtain fabrics for blocking sunlight:
| Fabric | Features |
|---|---|
| Canvas | – Made from dense cotton or linen – Heavy, thickly woven texture – Absorbs and blocks light extremely well |
| Brocade | – Intricately woven with raised floral/paisley designs – No open space between threads – Opaque and luxurious appearance |
| Wool | – Thick natural protein fibers – Opaque, absorbs light wavelengths – Insulating against cold and noise |
| Velvet | – Soft plush pile absorbs light – Luxurious look and feel – Can be made of silk, cotton, polyester, rayon or wool |
| Faux Silk | – Mimics look and feel of real silk – Tightly woven threads block light – Affordable alternative to silk |
Best Colors for Blocking Light
Rich saturated tones work best for keeping out sunlight. Recommended colors include:
- Black – The gold standard for room darkening and light absorption
- Navy – A softer alternative to black that still blocks light well
- Dark green – Rich forest greens absorb light wavelengths evenly
- Dark red – From maroon to burgundy, these block and absorb light
- Chocolate or dark brown – Warm, cozy earth tones that obscure sunlight
- Dark gray – Sophisticated charcoal grays block glare and rays
Aim for dark hues without a lot of white base or light sheen. The deeper and more saturated the tone, the better it will perform as a blackout curtain.
How to Use Curtains with Windows for Maximum Light Blocking
Achieving complete window blackout requires careful curtain installation and use. Here are some tips for blocking light with window curtains:
- Hang curtains above the window molding so the fabric overlaps the edges of the frame.
- For standard rods, extend curtain panels past the edges of the window by at least 2-3 inches on each side.
- Allow ample overlap where two curtain panels meet in the middle—at least 6 inches or more.
- Do not skimp on length. Curtains should be 2 to 2 1/2 times the height of the window.
- Use weights or magnetic strips to hold bottom hems in place and prevent light gaps.
- Close curtains tightly and evenly each time for consistent light blocking.
- Install a matching fabric valence above the curtain rod to cover top light gaps.
- Layer curtains and shades for added light blocking security.
With the right techniques, window curtains can transform a room into a dark cocoon free from unwanted sunlight and glare.
Conclusion
When shopping for new curtains, focus on finding options made from tightly woven opaque fabrics like canvas, velvet, faux silk or brocade. Dark saturated colors like black, navy and dark red provide superior light absorption and blockage compared to lighter shades. Added features like blackout linings, dense inter-lining, ripplefold pleats and rod pockets maximize coverage and prevent light infiltration around the edges.
Getting the perfect curtains to stop sunlight comes down to combining the right dense, thick fabrics with technical light blocking features and proper installation. With the curtains tailored to your windows and mounted flush with the frames, you can successfully blackout any room.
