Bagging is a faux painting technique used to give the wall the effect of marbling and depth.  This technique is relatively easy, compared to other faux painting techniques.

There are two different ways to bag a wall.  The first bagging technique involves taking a crumpled bag in your fist and dabbing or "stomping" the bag onto the wall.  Bagging using this technique will make small sunburst-type designs on your wall.  The second bagging technique involves taking a large plastic sheet (thin plastic drop cloths work well for this) and placing it against the glazed wall.  This will result in the entire wall appearing to flow like a giant slab of marble.

There are also two glazing techniques you will need to choose between.  One is positive glazing, and the other is negative glazing.  Essentially, the difference is, you are either putting glaze on (positive) or taking glaze off (negative).

The first thing you want to do is paint the wall the base color.  This is the color that will show through the bagging effect and basically be the background color.  Use eggshell or semi-gloss paint for your base coat.  This will allow the glaze you will use in the bagging effect to "slide."  Do not use flat paint as your base color.

Negative glazing will cause the wall to be predominantly the color of the glaze coat.  Brush or roll glaze in a complementary color over the painted wall either in sections, if you are using the "stomping" bag technique, or the entire wall, if you will be using the plastic sheet technique.

Negative Stomping Technique:

Glaze a section of the wall about the width of your outstretched arms.  While the glaze is still wet, ball a plastic bag into your fist and begin stomping into the glaze on the wall.  You are essentially pulling glaze from the wall with each stomp.  About every three stomps or so, wipe the excess paint off of your bag ball.  Complete the entire section with this stomping technique, then glaze the next section, stomp, and repeat.  Make sure to stomp over the section lines to eliminate them.

Negative Plastic Sheet Technique:

Glaze a large section of the wall in a section approximately the size of your plastic sheet.  While the glaze is still wet, place the plastic sheet against the glazed wall, effectively covering the entire section you just glazed.  Lightly pat the plastic sheet down to remove large air bubbles, but don't pat or flatten the plastic sheet too much, as the wrinkles and small air pockets are what create the marbling effect.  Make sure to get into the corners of the wall, or you will have obvious places where the glaze will not be marbled.  Once the entire plastic sheet is patted down lightly, pull the plastic sheet from the wall.  Move on to the next section, paying particular attention to overlapping a little on the previously glazed section to avoid having a definite line between the sections.

Positive Stomping will cause the finished wall to be predominantly the base color.  In positive glazing, you will be putting glaze onto the wall, rather than taking it off.

Positive Stomping Technique:

Pour the glaze into a paint pan.  Ball a plastic bag into your fist and dab the bag ball into the glaze.  Stomp the glaze onto the painted wall using a dabbing technique.  Continue until the entire wall is stomped.

Positive Plastic Bag Technique:

This technique is by far the most difficult, because working with the plastic sheet with the glaze on the sheet is difficult.  You will need at least one other person to help with this technique.

Spread the plastic sheet out onto a tarp or drop cloth.  Place bricks or something heavy on all four corners to hold the sheet down.  Roll the glaze onto the plastic sheet in a smooth, thin coat, covering the entire sheet.  With a person on either end of the plastic sheet, lift the wet glazed plastic sheet and place it against the wall.  Gently smooth out large air bubbles.  Make sure to get into the corners of the wall, or you will have obvious places where there is no glaze.  Remove the plastic sheet and repeat the process until the entire wall is bagged.  Again, overlap slightly so there will be no obviously lines between the sections.

It is possible to use more than one color of glaze.  If you choose to do so, you'll have to make yet another technique choice.  If you glaze the first color and let it dry before you glaze the next color, you will have more definition between the colors.  If you choose to glaze two or more colors while they are wet, you will get a more mottled Monet-esque style as the wet colors will blend and mix.

Have fun and make up your own faux painting technique.  Use leaves, feathers, or other "found" items to create designs and depth on your wall.

Most of all, have fun!