Abstract:
An aqueous liquid solution containing soluble salts of coloring metals—particularly manganese and ferric iron along with a sugar source and fulvic and/or humic acid can be readily applied to galvanized metal surfaces impart a natural color tone to such surfaces. In this manner the visibility manmade structures like fences and guardrails is quickly and easily reduced and readily blended into the natural background. The liquid solution can be readily sprayed on galvanized surfaces. When the ambient temperature is warm natural color will develop two-three weeks.

Description:
CROSS-REFERENCE TO PRIOR APPLICATIONS 
     The present application is a continuation-in-part of and claims the benefit of U.S. non-provisional application Ser. No. 12/370,493, filed on Feb. 12, 2009, now issued as U.S. Pat. No. 8,075,684, which claims the benefit of U.S. provisional application No. 61/028,987, filed on Feb. 15, 2008. 
    
    
     U.S. GOVERNMENT SUPPORT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Area of the Art 
     The present application is in the art of landscaping and is directed to a product and method for making galvanized metal structures blend into the surrounding terrain. 
     2. Description of the Background Art 
     New construction particularly when exposed rock and soil surfaces are altered often fails to harmonize with the surrounding terrain because altered surfaces are colored differently than the native surfaces. When the construction contains concrete and metal (iron and steel) components, the new concrete and metal may also present a harsh appearance in spite of the use of concrete coloring agents and metal covering paints. These problems are exacerbated in relatively arid regions like the Southwestern portion of the United States both because the aridity slows the growth of natural vegetation that will in time cover the altered surfaces, and because in relatively arid regions rock surfaces are naturally covered with “desert varnish” a coating that is often much different in color than the “naked” rock surface. The presence of the “desert varnish” makes any alteration to the rock surface that much more obvious. 
     Because natural coloration to rock surfaces such as “desert varnish” develops slowly over a period of years or even decades or longer, there have been efforts to apply materials to more rapidly mask alteration to the surface so that new construction can more rapidly blend in. The most commonly used approach has been to apply coloring liquids not unlike paints or stains used on wood. Commercially available formulations of paint-like materials available for coloring rock surfaces tend to be superficial and, thus, are readily weathered, commonly fading within as little as a few months. Such liquids gain most of their tinting or coloring power from blending a dye or pigment into a liquid carrier or vehicle such as latex, oil or organic solvent. With even minimal weathering from ambient sunlight, wind or rain such a superficial coating may readily slough from the treated surface and/or the pigments may fade or change hue. Further, because the coloring agent&#39;s primary means of attachment to the rock or other surface relies almost entirely upon surface adhesion, the bond between the color and the surface is at best weak and lacks the permanence that is desired. 
     There have been attempts to more closely replicate naturally developed surface coloration. U.S. Pat. Nos. 4,725,451 and 4,812,340 to Cripe describe a method of simulating “desert varnish” by first reacting the rock surface with a liquid alkali base and then applying a coloring layer of a metallic salts such as iron or manganese salts. U.S. Pat. No. 5,308,646 to Moore discloses a method of applying metal acetate salts to rock surfaces to mimic “desert varnish.” This reference particularly prefers the application of iron acetate and manganese acetate. Iron salts are known to impart reddish “rust” colors when they become oxidized. Manganese oxide is black/purple and is believed to be a principle coloring agent in natural “desert varnish.” Recent research has confirmed the presence of manganese in “desert varnish” but has also surprisingly revealed that a major constituent of natural “desert varnish” is clay powder apparently from a wind blown source. It is also known that lithophilic bacteria inhabit the surface layers of rocks are at least partially responsible for the process that binds the clay particles and oxidizes the manganese ions to form natural “desert varnish.” 
     SUMMARY OF THE INVENTION 
     Natural surfaces can be imparted with a natural color by utilizing metallic coloring agents to create a chemical bond between substrate rock, soil, concrete or metal and the coloring agent. The strength and permanence of the bond is improved by selecting forms of the coloring agent from various soluble and reactive salts of color generating elements such as nitrate salts. The parent application of this application was primarily direct towards coloring rock (including concrete) surfaces although use of the formulation on metallic surfaces was contemplated. The present invention is a refinement of the original formula that is particularly effective in coloring galvanized metal (usually steel) surfaces. In addition, methods for achieving optimum results in coloring galvanized surfaces have been developed. 
     Salts of pigment forming elements such as iron, copper, cobalt and manganese are advantageously used. A large number of other color or pigment producing metals such as “rare earths” elements and can be used. Salts that are oxidizing agents appear to contribute to a bond between coloring agent (metal atom) and substrate increasing tenaciousness and resulting in greater permanence. The final shades and hues of pigmentation visible to the human eye result from an interaction between the substrate (possibly by means of an oxidizing event) and the coloring metal atoms. 
     Some of the soluble organic compounds used with the metallic coloring agents are complexing agents such as fulvic acid, ulmic acid, citric acid, malic acid, etc). These agents chelate and complex the metal ions to enhance their solubility beyond that provided by anions (as explained below). In particular fulvic and ulmic acids which are complex humic substances have color of their own and also serve as binding materials that can help immobilize the color-forming metal ions. 
     The basic formula contains an effective concentration of soluble salts of color producing metals. Iron and manganese salts are particularly preferred and an effective formula should contain at least one of these metals. The preferred anion is nitrate but other soluble anions as mentioned herein can be used. A soluble anion that is an oxidizer is preferred. The soluble metal ions are combined with an organic sugar energy source. The preferred material is high fructose corn syrup although glucose syrup or sucrose solutions are also effective. The choice of type of sugar is largely economic although high fructose syrup and sucrose syrup tend to have a lower viscosity (favorable characteristic) than glucose syrup. 
     At least one organic complexing agent is also required in the formula. The favored agents are fulvic acid and humic acid. For a single complexing agent fulvic acid is preferred. A variety of trace elements are preferably included to promote growth of organisms, and humic acid also serves as a trace element source. In addition, a preservative is added because of the large amount of sugar. Propionic acid is a preferred preservative. In modifying the original formula to achieve optimal results with galvanized metal surfaces increasing the concentration of certain metallic ion coloring agents—namely manganese and ferric iron—and of fulvic acid has proven particularly effective. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventors of carrying out their invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the general principles of the present invention have been defined herein specifically to provide an improved formula for producing natural “aged” coloration to unpainted galvanized metal surfaces. 
     The present invention utilizes the chemical activity of metallic coloring agents to create a chemical bond between substrate rock, soil, concrete or metal and the coloring agent. The strength and permanence of the bond is improved by selecting forms of the coloring agent from various soluble and reactive salts of color generating elements. Examples of these soluble salts are primarily nitrates and chlorides although other soluble anions such as chlorates are useful as well. The effective salts are those of metallic pigment elements such as cobalt (e.g., cobaltous chloride), copper (e.g., copper nitrate), iron (e.g., ferric nitrate) and manganese (e.g., potassium permanganate, manganese nitrate). 
     A large number of other color or pigment producing metals also exist—many of them being “rare earths” elements and can be used in the general formula given below. Many of these compounds are oxidizing agents and such materials appear to contribute to a bond between coloring agent (metal atom) and substrate increasing tenaciousness and resulting in greater permanence. The final shades and hues of pigmentation visible to the human eye result from an interaction between the substrate (possibly by means of an oxidizing event) and the coloring metal atoms. Thus, because of the often, inhomogeneous make-up of the substrate rock, the final outcome will demonstrate highly variable shades and hues with a depth of variation, creating a product of non-repetitive, surprisingly beautiful and natural looking outcome. In the case of galvanized metal such as guard rails or fences, the newly installed metal has a bright, silvery appearance that really stands out. Left to its own devices the shiny zinc will eventually develop a coating of zinc oxide so that the metal will lose much of its shine. However, the color remains light and does not blend harmoniously with natural scenes. In a proper formulation the pigment producing metals will develop a warm brownish color on a galvanized surface. Such a color helps blend the galvanized surface into the natural background. 
     The primary aim of these unique formulations for rock and surface coloration is to permeate 1-10 mm or more into the surface of the target object (usually rock or concrete—i.e., artificial rock). In the case of a metal surface, penetration is necessarily less. 
     High solubility of the staining compounds is an important requirement. For example, the cold water solubility of Ca (NO 3 ) 2  is equivalent to &gt;10,000 lbs in 500 gallons of water at 65° F. (or &gt;2.4 Molar solution). Other nitrate salts tend to have high solubilities. High solubility ensures that the active materials are able to penetrate relatively deeply into the rock (or other substrate). To create also subtle to distinct variations in staining, we have, in most formulations, included various carbohydrates, amino acids, proteins and other carbon-hydrogen-oxygen containing materials. These materials works in at least two ways. First, the presence of organic material provides nourishment for various species of “epiphytes” (organisms which live on the surface of the substrate). For example, we have demonstrated that a spray containing these agents enhances bloom of various algal and lichen species. Such a bloom always adds another dimension of artistry to the overall staining effect since the algae and lichens are colored themselves. In addition, the organic materials support the growth of lithophilic bacteria which live both on and within the surface layers of the substrate. All of these living organisms tend to secrete compounds that digest or alter the rock surface—thereby enhancing the ability of the staining compounds to penetrate. Second, the organic materials secreted by bacteria can act as vehicles to bind the coloring agents within the substrate. Organic compounds in the stain solution act in a similar fashion to form a precipitate or vehicle that further binds the coloring agents. This is particularly important in creating a coating on a metal surface where penetration is necessarily extremely limited. 
     Some of the soluble organic compounds used with the metallic coloring agents are complexing agents such as “humic acids, fulvic acid, ulmic acid, citric acid, malic acid, etc.). These agents chelate and complex the metal ions to enhance their solubility beyond that provided by anions. In particular fulvic and ulmic acids which are complex humic substances have color of their own and also serve as binding materials that can help immobilize the color-forming metal ions. 
     To better appreciate the importance of the solubility of the metal ion coloring agents, an extremely soluble substance, calcium nitrate, will be used as an example. It will be apparent to one of skill in the art that calcium ions are not normally considered to be color formers. However, calcium nitrate is extremely soluble thereby permitting penetration into the surface of the substrate. After the calcium ions penetrate, they can be rendered insoluble and the matrix formed by insoluble calcium ions can help bind other metals which are direct color formers. The steps of the process are as follow: 
     1. Ca(NO 3 ) 2 +H 2 O→Ca ++ +2NO 3   −   
     The strong oxidizing power of the nitrate group helps ensure that calcium is in a cationic form. 
     2. Ca ++ +2NO 3   − +SO 4   −− +2Na + →Ca SO 4 +2(Na NO 3 ) 
     When the solution is sprayed onto a surface, the high solubility of the compounds helps to keep them in a reactive, ionic form. This, then allows the sulfate anion of sodium sulfate (in this example) to interact with the calcium ions to form the relatively insoluble calcium sulfate. The results are shown here as sodium nitrate, but that salt is actually quite soluble and would most likely be leached away by precipitation or ground water. Although calcium does not provide color, inclusion of soluble calcium salts (about 0.05M to about 0.5M) can result in formation of an insoluble matrix that helps trap color forming agents. Similar precipitation will occur if other less soluble anions (such as CO 3   −− ) interact with the cations. 
     Also, many of the color forming metal ions will be precipitated or rendered insoluble by a redox reaction. For example, the permanganate ion (MnO 4− ) is quite soluble, but if this group is reduced (gains electrons) by interaction with organic matter or bacterial electron transport, it can be converted to insoluble manganese dioxide (which is black in color). Similar redox reactions can result in precipitation of other color forming metal ions. Thus, the addition of various organic compounds to the mixture enhances color formation by promoting bacterial growth which leads to reduction of color forming metal ions and by direct redox reactions of the color forming metal ions. 
     Additional coloring can be achieved through mixing the components and varying the concentration of the spray solution. Spraying the target rocks, metal or concrete at varying temperatures yields variations in the absolute color and intensity of the color effects. Another very important factor in the spray design allows the spray to thoroughly wet the target surface. 
     The basic formula contains an effective concentration of soluble salts of color producing metals. Iron and manganese salts are particularly preferred and an effective formula should contain at least one of these metals. The preferred anion is nitrate but other soluble anions as mentioned herein can be used. A soluble anion that is an oxidizer is preferred. The soluble metal ions are combined with an organic sugar energy source. The preferred material is high fructose corn syrup although glucose syrup or sucrose solutions are also effective. The choice of type of sugar is largely economic although high fructose syrup and sucrose syrup tend to have a lower viscosity (favorable characteristic) than glucose syrup. It is believe that the major function of the sugar energy source is to support the growth of microorganisms that promote the oxidation and coloration. However, the sugars may also function directly in the chemical reactions. At least one organic complexing agent is also required in the formula. The favored agents are fulvic acid and humic acid (humic acid or humic materials is often a catchall term which includes fulvic and ulmic acid as well as other compounds). The mineral Leonardite is a humic mineral that is the source of trace elements as well as humic acid type materials. For a single complexing agent fulvic acid is preferred. A variety of trace elements are preferably included to promote growth of organisms, and humic acid also serves as a trace element source. In addition, a preservative is added because of the large amount of sugar. Propionic acid is a preferred preservative. 
     A typical formula might contain 0.4M Magnesium, 0.2M Zinc, 0.4M Manganese, 0.3M Iron, 0.04M Copper, 0.008M Cobalt, 0.003M Molybdenum, and 0.02M Boron as well as other active ingredients as shown in the table. However, as indicated in Table 1, below, there can be a considerable effective range of some of the ingredients. This formula can be used either undiluted or diluted as much as 1 part in 40 parts water depending on the color intensity of the desired results. 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Typical 
                   
               
               
                   
                 Range 
                   
               
               
                   
                 (Molarity or 
                   
               
               
                   
                 amount per 
                   
               
               
                 Ingredient 
                 100 gallons) 
                 Comments 
               
               
                   
               
             
             
               
                 Water 
                 Sufficient to 
                 (The target water to total 
               
               
                   
                 make 100 
                 volume is between 1:3 
               
               
                   
                 gallons 
                 and 1:4) 
               
               
                 Propionic Acid 
                 0.0003M-0.0015M 
                 Preservative and 
               
               
                   
                   
                 extracts micronutrients 
               
               
                 Humic Acid 
                 0.5-5.0 lbs 
                 Complexing/chelating 
               
               
                 (Leonardite) 
                   
                 and provides a variety of 
               
               
                 [micro-nutrient 
                   
                 trace elements 
               
               
                 source] 
                   
                   
               
               
                 85% Fructose 
                 0.5-10 gallons 
                 Promotes growth of 
               
               
                 (High Fructose 
                   
                 epiphytic algae, bacteria 
               
               
                 Corn Syrup) 
                   
                 and lichens 
               
               
                 2% Fulvic Acid 
                 2.5-20 gallons 
                 Complexing/chelating 
               
               
                 Solution 
                   
                 agent and trace 
               
               
                   
                   
                 elements 
               
               
                 Magnesium 
                 0.05M-0.55M 
                 Contributes to growth of 
               
               
                 Nitrate 
                   
                 microorganisms 
               
               
                 Zinc Nitrate 
                 0.0026M-0.52M  
                 Imparts strong oxidation 
               
               
                 (Solution) 
                   
                 of rock-contained 
               
               
                   
                   
                 ligands; brownish 
               
               
                   
                   
                 coloration 
               
               
                 Manganese 
                 0.02M-0.5M  
                 Oxidizer and source of 
               
               
                 Nitrate (Solution) 
                   
                 purple-black coloration 
               
               
                 Ferric Nitrate 
                 0.02M-0.5M  
                 Oxidizer and source of 
               
               
                 (Solution) 
                   
                 red-brown coloration 
               
               
                 Cuprous Nitrate  
                 0.008M-0.08M  
                 Oxidizer and source of 
               
               
                 (Solution) 
                   
                 blue-green coloration 
               
               
                 Cobalt Nitrate 
                 0.003M-0.05M  
                 Oxidizer and source of 
               
               
                   
                   
                 red coloration 
               
               
                 Sodium 
                 0.0015M-0.025M  
                 Essential nutrient for 
               
               
                 Molybdate 
                   
                 epiphytes; orange-yellow 
               
               
                   
                   
                 coloration 
               
               
                 Sodium 
                 0.002M-0.03M  
                 Essential nutrient for 
               
               
                 Tetraborate 
                   
                 epiphytes 
               
               
                   
               
             
          
         
       
     
     Directions for mixing a 100 gallon batch: 
     1. Fill a holding tank or barrel with the required amount of Propionic Acid+40 gal water and soak the humic acid micronutrients (crumbled to 20-mesh or less particles) to extract essential micro-nutrients. A painter&#39;s filter sack can be used as a “tea bag” to contain the humic acid for extraction. 
     2. Fill the mix tank with 180 gal warm water (approximately 85-115° F.)+the required amount of Fulvic Acid solution and blend thoroughly with agitators running before adding the solution from step 1. 
     3. Gradually blend in: Magnesium Nitrate (as a stock solution), Zinc Nitrate (as a stock solution, Manganese Nitrate (as a stock solution, Ferric Nitrate (as a stock solution), Cuprous Nitrate (as a stock solution) and continue to homogenize thoroughly. 
     4. Gradually add the Cobalt Nitrate solid and dissolve completely, then follow the Sodium Molybdate solid and add Sodium Tetraborate solid last. Continue to agitate and blend until all materials are in solution. Gradually add the required amount of high fructose corn syrup and blend thoroughly. Add water until target volume of 100 gallons is reached. 
     5. Filter through 400 mesh screen and store in a tote until bottled. 
     The propionic acid is a preservative to prevent growth of microbes during storage as well as an agent to extract micronutrients. Other preservatives such as benzoic acid, citric acid or sorbic acid can be used; citric acid also acts as a complexing agent. However, because part of the goal of the material is to promote bacterial, algal and fungal growth on the substrate to be colored, strong biocides should be avoided. Humic acid micronutrients serve to supply micronutrients for promoting biological growth. In addition, the humic acid is a chelator and organic binding agent (i.e., contributes to an insoluble matrix). Fulvic acid serves a similar purpose. Magnesium nitrate and sodium tetraborate are nutrient compounds with oxidative properties. Although inherently colorless they can contribute to the precipitated matrix material to trap the colored metallic elements. Zinc nitrate contributes to brownish tones; manganese nitrate contributes to purple and black tones; ferric nitrate contributes reddish or brownish tones; cuprous nitrate contributes to bluish and greenish tones; cobalt nitrate provides reddish tones; and sodium molybdate provides orange and yellowish tones. It will be apparent that the exact proportion of the coloring agents can be varied to better match certain types of native rocks or soils. This mixture is a good general purpose stain for a variety of normal rock tones. 
     Besides the major coloring agents mentioned above, a large number of other metal ions can be included for special purposes as long as the oxidizer/organic energy source/fulvic acid scheme is followed. In particular, small quantities of soluble rare earth elements (elements from the Lanthanide and Actinide series) can be added to modulate the color. Since these elements are expensive and in some cases toxic, they should be used judiciously. 
     Application to Surfaces: 
     Depending on quantities of material to be applied and type of surface area to be treated, i.e. rock, concrete, or steel various application devices can be used. For example, a commercial type hand held or backpack sprayer (1-3 gal capacity) can be used for smaller areas (up to about 1,000 square feet). Also, smaller more controlled applications for example, (naked or untreated) rock that is positioned next to decorative stone that is not to be treated can be done with paint brushes and sponge brushes of all sizes. This provides more detailed control when applying material to the surface to be treated without the having danger of overspray or drift (typical from a spray device) that might cause material to be applied on surfaces that were not intended to be treated. Taping off (masking) areas not to be treated is also an option but is cumbersome and increases overall application time. 
     When applying the material (with any of the application methods) the applicator generously and completely covers the surface to be treated. Runoff may occur and can be evened out with either a sponge or terry cloth rag. Blending and soaking the excess material evenly will eliminate color runs that might develop and look unnatural. 
     Color Transition and Development: 
     During the warm summer months initial color cure time will normally take 4-8 days depending on sunlight and heat intensity. Cold winter months typically take at least twice as long, about 10-20 days or more depending again on sunlight and heat intensity. If rain falls or other water intrusion, i.e. irrigation, water truck, etc. occurs during this process it may prolong the color development time or even necessitate reapplication of the product to reach target color. During color transition and development the active ingredients penetrate into the rock surface where chemical and biological reactions cause the color to develop and become fixed in place. 
     The precise color characteristics depend on the types and amounts of metal ions used. The following description is based on the example formula given above. The final color hue reached is dependent on surface type, but typically immediately after applying the material a yellowish orange will appear for a few days depending on time of year. After a period of days the surface color will then transition from a yellowish to orangey rust color and remain like that for a few more days. The final color transition is from orangey rust to earth tone browns, light, medium, and dark depending on the concentration of the initial application. 
     Formulations for Galvanized Metal 
     A number of experiments have been carried out concerning coloring galvanized metal (generally steel). It was discovered that the original formula described above has some power to color galvanized surfaces. In a way this is somewhat surprising. The ability of the formula to color iron or steel directly is not so surprising because the formula might be expected to promote surface oxidation. However, while the formula can impart iron or steel surfaces with a brown color, this does not appear to be rust or at least not entirely rust. One would expect, however, that a galvanized surface would avoid oxidation—at least of the type that would impart surface color. However, the formula is able to impart a brownish tone even to galvanized surfaces. It has been discovered that the ability to color galvanized surfaces can be significantly enhanced by increasing the amount of manganese and ferric iron as compared to a formula optimized for coloring rock surfaces. 
     For example, Table 2, below, compares the amounts of some key active ingredients of a formula optimized for use on rocks with one optimized for coloring galvanized metal. It should be noted manganese is significant increased, and iron is increased somewhat. The ratio between iron and manganese is adjusted to obtain the desired final color. Iron favors red/red-orange tone while manganese favors gray/black tone. The illustrated formula produces a fairly dark neutral brown color. Zinc, copper, boron, cobalt and molybdenum are at lower concentrations in the galvanized metal formula. This is a result of dilution from adding manganese and iron (and fulvic acid, see below) to the original formula. There is no evidence that increasing or decreasing the concentration of these ingredients either helps or hinders coloring galvanized metal. The other ingredients (as listed in Table 1) remain the same between the two formulae except for the dilution effect noted. However, the amount of fulvic acid is significantly increased to at least twice that of the rock staining formula. It appears that increased fulvic acid contributes to the more rapid formulation of a colored film on the galvanized metal. This material was produced by taking 62.5 gallons of the original rock formula and adding to it 50 gallons of 10% ferric nitrate, 125 gallons of 12% manganese nitrate solution and 12.5 gallons of 2% fulvic acid solution. 
     
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 comparison of galvanized metal and rock staining formulae: 
               
             
          
           
               
                   
                 Ingredient 
                 Rock Formula 
                 Galvanized Metal Formula 
               
               
                   
                   
               
               
                   
                 Magnesium 
                  0.5% 
                 0.125% 
               
               
                   
                 Manganese 
                  1.75% 
                  3.0% 
               
               
                   
                 Zinc 
                  0.75% 
                  0.2% 
               
               
                   
                 Iron 
                  1.1% 
                  1.25% 
               
               
                   
                 Copper 
                 0.125% 
                 0.032% 
               
               
                   
                 Boron 
                  0.01% 
                 0.003% 
               
               
                   
                 Cobalt 
                 0.025% 
                 0.007% 
               
               
                   
                 Molybdenum 
                 0.015% 
                 0.00375 
               
               
                   
                   
               
             
          
         
       
     
     Application of the Galvanized Metal Formula 
     The galvanized metal formula can be applied by spraying the liquid to metal structures (e.g., guard rail or fencing) in situ. However, it there must be 3-6 weeks of warm, dry weather for optimal color to develop. As might be expected, application to metal surfaces is particularly vulnerable to rain which simply washes the formula off before it is cured. When curing is complete, the color is present as a durable surface layer. While strong abrasion can remove the color and expose the underlying metal, simple rubbing or contact will not disturb the color. 
     In view of the vulnerability to weather, experiments were undertaken to explore ways to accelerate the curing of the color. In rock applications, it is believed that both temperature and exposure to light play roles in the development of the color. However, with application to galvanized metal, it appears that temperature is more critical. In one set of experiments galvanized metal samples were dipped into the formula for times ranging from 5 to 30 minutes. The dipped metal was allowed to drip dry and then was baked in an oven at temperatures ranging from 250-350° F. for times ranging from 20 minutes to one hour. All of these treatments produced a nice color equivalent to at least a two week outside curing during warm, dry summer weather. After this treatment, the coating was weather proof. However, baking in a 150° F. oven for this amount of time produced a somewhat lighter color that was judged as suboptimum. It is not know if longer baking at 150° F. would obviate this problem. It does appear as if optimum processing (relatively short time at the lowest possible temperatures) is achieved at oven temperatures between about 250-350° F. Higher temperatures do not appear to improve results. Clearly, light is not required for color production on metal surfaces. 
     Another approach is to quench the hot metal immediately as it leaves the galvanizing “bath” (molten zinc) at about 700° F. However, this did not result in adequate color development. Either the quenched metal cools below the critical temperature too rapidly, or drying is a necessary part of color development. Soaking the metal in a bath of heated formula does, however, result in relatively good color development suggesting that drying is not always necessary. The soaking experiments were carried out at bath temperatures between 110-130° F. It is thought that slightly lower temperature (e.g., 100° F.) may somewhat be effective, but at temperatures of 130° F. and above the stability of the formula in the bath is impaired (e.g., precipitation occurs). It appears that higher application temperatures result in better color, but bath stability is limiting. It is also possible to apply a hot spray using a device that heats the formula as it is sprayed to avoid the stability issues. Also, it seems likely that combinations of hot spray and oven baking may produce optimum results. Baking with or without hot spray application is favored in a factory setting where the items are colored before installation. Hot spraying is favored for in situ application where the spraying might also be combined with heat guns or hot air blowers to result in rapid setting and coloring of the applied material. 
     The following claims are thus to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, what can be obviously substituted and also what essentially incorporates the essential idea of the invention. Those skilled in the art will appreciate that various adaptations and modifications of the just-described preferred embodiment can be configured without departing from the scope of the invention. The illustrated embodiment has been set forth only for the purposes of example and that should not be taken as limiting the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.