what is the technique or method used to resurface the brick exterior
of my house,which is now red, by "mortar washing" the surface with a
colored slurry of mortar in order to change the color of the brick
exterior while preserving the underlying brick outline?

Hi pedro2x,

According to the Architectural Dictionary
http://www.dreamghar.com/bdic.html
the process of rubbing cement mortar over the face of brickwork using
sacking is known as "bagging" or "bag rendering". It can be painted if
desired.

"Bagging is the application of a mortar mix to flush jointed brickwork
with a hessian bag and produces a rough texture through which the
brick pattern is evident."

Design in Brickwork
http://www.brickbydesign.com/brickwork-design/coatings/

The "Backyard Blitz" site describes the process:

"Create a mortar mix the consistency of thick cream (6:1 brickies
sand:cement). Wet the entire surface of the brickwork to be bagged
(reduces cracking). Use a large sponge to apply the mix to the
brickwork ... Bagging can be done with a piece of hessian sack to give
a rough effect, a sponge for a medium effect or a soft cloth for a
smoother effect. Allow the bagging to dry, then paint."

Step by Step Construction
http://www.burkesbackyard.com.au/blitz/step_by_step_construction

Pigments can be added to the mortar to achieve the desired color.
Alternatively, a proprietary acrylic-based render can be used to
achieve a greater range of colors, increased weather resistance and a
lower-maintenance finish. One such render is EcoStyle Portofino:

ecoportofino
http://www.rockcote.com.au/technical/ecoportofino.html

The application of Portofino is described, then stated to be a
specialist procedure. But the manufacturer's advice to first rub down
the brickwork with a block (to remove any mortar or foreign materials
"proud" of the surface) would be good advice for any kind of bag
rendering.

Here's some information on colored mortar:

Masonry Magazine: The Art of Coloring Mortar
http://www.masonrymagazine.com/5-03/bricksb2.html

and the following page has links to data sheets for mortar pigments:

Pigments - Colored Mortar
http://www.bayferrox.bayerchemicals.com/bayer/chemicals/ipg.nsf/id/969E3657589E7488C1256CB4007BB2D1

Finally, here's an illustrated guide to bagging bricks:

BHG Australia - Bagging bricks
http://www.bhg.com.au/home_improvement.nsf/Content/Plans+and+Projects+-+TV+-+Bagging+Bricks?openDocument

You may have noticed that quite a few of these links are to Australian
websites. That's because brick bagging is a popular finish for both
new construction and renovation in Australia.

Good luck with your project!


Google search strategy:

brick mortar +bagging
://www.google.com/search?q=brick+mortar+%2Bbagging

"bag rendering" brick
://www.google.com/search?q=%22bag+rendering%22+brick

"colored mortar"
://www.google.com/search?q=%22colored+mortar%22


Regards,
eiffel-ga