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sarah h 06-28-2008 02:28 PM

STUCCO-Part2: How Stucco is Made
 
Here are some different ways to make stucco, if you can't find it ... if you try any of these, however, just remember that lime is very caustic, most especially quick-lime, which can even explode if you add water to it, rather than adding it to the water. Stick with the hydrated lime - unless you know what you are doing, there are all sorts of issues.

Anyway, here goes:

Historic Stucco Mixes
Historic stucco mixes varied a great deal regionally, depending as they did on the availability of local materials.

Materials Specifications are as follows:
Lime should conform to ASTM C207, Type S, Hydrated Lime for Masonry Purposes.
Sand should conform to ASTM C144 to assure proper gradation and freedom from impurities. Sand, or other type of aggregate, should match the original as closely as possible.
Cement should conform to ASTM C150, Type II (white, nonstaining), portland cement.
Water should be fresh, clean and potable.
If hair or fiber is used, it should be goat or cattle hair, or pure manilla fiber of good quality, " to 2" in length, clean, and free of dust, dirt, oil, grease or other impurities.
Rules to remember: More lime will make the mixture more plastic, but stucco mortar with a very large proportion of lime to sand is more likely to crack because of greater shrinkage; it is also weaker and slower to set. More sand or aggregate, will minimize shrinkage, but make the mixture harder to trowel smooth, and will weaken the mortar.


Vieux Carre Masonry Stucco
Base Coats (2):
1 part by volume hydrated lime
3 parts by volume aggregate [sand]--size to match original
6 pounds/cubic yards hair or fiber
Water to form a workable mix,
Finish Coat:
1 part by volume hydrated lime
3 parts aggregate [sand]--size to match original
Water to form a workable mix.
Note: No portland cement is recommended in this mix, but if it is needed to increase the workability of the mix and to decrease the setting time, the amount of portland cement added should never exceed 1 part to 12 parts lime and sand.
("Vieux Carre Masonry Maintenance Guidelines," June, 1980.)

Soft Brick Mortar and Soft Stucco
5 gallons hydrated lime
10 gallons sand
1 quart white, nonstaining portland cement (1 cup only for pointing)
Water to form a workable mix.
(Koch and Wilson, Architects, New Orleans, Louisiana, February, 1980)

Natural Cement or Hydraulic Lime Stucco
1 part by volume hydrated lime
2 parts by volume white portland cement
3 parts by volume fine mason's sand
If hydraulic lime is available, it may be used instead of lime-cement blends. ("Conservation Techniques for the Repair of Historical Ornamental Exterior Stucco, January, 1990)

Early twentieth century Portland Cement Stucco
1 part portland cement
2 parts sand
Hydrated lime = to not more than 15% of the cement's volume
Water to form a workable mix.
The same basic mix was used for all coats, but the finish coat generally contained more lime than the undercoats. ("Illinois Preservation Series No. 2: Stucco," January, 1980)

American Portland Cement Stucco Specifications (c. 1929)
Base Coats:
5 pounds, dry, hydrated lime
1 bag portland cement (94 lbs.)
Not less than 3 cubic feet (3 bags) sand (passed through a #8 screen)
Water to make a workable mix.
Finish Coat:
Use WHITE portland cement in the mix in the same proportions as above.
To color the stucco add not more than 10 pounds pigment for each bag of cement contained in the mix.

brokencookie 06-28-2008 04:33 PM

Re: STUCCO-Part2: How Stucco is Made
 
Thanks Sarah
This information is very helpful for those of us considering stucco.

Bruce

Ken524 06-28-2008 06:12 PM

Re: STUCCO-Part2: How Stucco is Made
 
Thank you Sarah! Great research.

I'm not into mixing my own sand, lime, portland. Can anyone recommend off the shelf products for scratch, brown and finish coats?

What about coloring? Should we add pigment to the finish coat or paint? What kind of paint?


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