Even though today's blackout curtains are very stylish and effective, they cannot compare to the effectiveness of room darkening shades. This is due to two factors: the way shades are mounted compared to the way curtains are hung, and the materials of the shades themselves.
Shades are typically hung inside the frame of the window itself, rather than mounting in front of the window. This means that they need to be measure to fit precisely. But it also means that there is no bleeding of light around the top like there can be with room darkening curtains.
There are two general styles of shades: roller and pleated. And pleated shades come in normal pleats or what is called 'honeycomb' pleats.
The roller-style room darkening shades have been around for a very long time. These are the types of shades you see in the old cartoons which, when pulled down slightly, release the catch which lets them stay down. The spring in the roller will cause the shade to zip up quickly (and pop out of the mount) if you let it slip from your hand. (Thus the cartoon-usage, when the shades would zip up and flap around on the spool.)
The nice thing about room darkening roller shades is that they are generally inexpensive. And for the money, they are one of the most effective methods for blocking out light and creating privacy. The materials are almost always thick enough to block 100% of the light. The downside is that even the nice ones are usually made of materials that are rather cheap. In addition, they can be ugly.
That's where pleated shades shine. (Pardon the pun.) The good-quality pleated shades are very attractive. They come in a wide range of colors and fabric choices which make it easy to match your decor.
When trying to block out light, the honeycomb shades are the best type of pleated shade to buy. Some pleated shades are a single-layer thick. This allows light to pass through all but the most opaque fabric, and through the holes where the line is threaded through the pleats. The honeycomb variety are a minimum of a double-layer of fabric, blocking more light, even where the draw lines are connected to the shades.
The final variety of room darkening shades are also called Roman Shades. They are somewhat of a blend between shades and curtains, and will be discussed in another post.Christy - Room Darkening Curtains info from http://roomdarkeningcurtains.net