Arc & spot welding
Automotive hand tools
Car enamel colors
Car paint colors
Car paint glossary
Car painting problems
Cleaning car upholstery
Infra-red paint drying
Interior automotive trim
Painting over paint
Paint surface preparation
Refinishing paint tips
Safe car spraying
Sanding, striping, rubbing
Shrinking sheet metal
Not finished yet:
Having determined the original color of the finish, take a suitable quantity of the right shade of lacquer and mix thoroughly. Failure to get all of the pigment thoroughly mixed will result in a different shade from the original finish.
Spray the damaged spot with a light coat of this lacquer. When dry, spray the next coat so as to overlap the first coat. When this dries, spray on a mist coat of thinner to blend the edge of the lacquer coat with the original finish.
If possible, let this dry over night. Then rub down the whole section. If the damage was in a fender, polish the whole fender. If in a body panel, polish the whole panel. In fact, some shops prefer to relacquer the whole panel or fender. In this way they get a better match with the color. Or more correctly, any slight difference in shade is not so noticeable when a complete panel or fender is done over.
Following is the step-by-step procedure as recommended by Du Pont for refinishing repair work.
Touch up and repair work operation
There are two ways of matching colors : buy them ready mixed or mix them yourself. But even if you prefer to buy ready mixed colors, it may not always be possible to do so. For that reason it is highly important to have authentic color mixing information available.
The color of a car on the road for several months cannot be accurately matched up through any standard stock of colors because of the changes that take place upon aging, and thus a perfect match for the original color is not a match for the motor car that has seen service on the road.
Repaint shops have therefore found it economical and profitable to make their own color matches, giving immediate attention to their customers, and yet not have a large stock investment in color.
The above information is common knowledge to every repaint shop, and the individual paint shop has been attempting to meet this condition by matching the shades on the repair jobs to the best knowledge that has been available up to this time.
In spite of this careful work, every one is familiar with the unsatisfactory jobs that come back after several weeks or months, showing fading, change of shade, or in some other way an unsatisfactory condition.
So here are some definite and simple rules for color mixing that will aid the shop craftsman in obtaining the colors that are necessary.
To begin with, it must be recognized that all colors are only relatively permanent. There are no colors that can be considered absolutely fast; therefore the auto painter must know which colors are most permanent and exactly where and when he may use the brighter, but less permanent shades.
There are many ways for arriving at the same shade or tone of color, yet it is highly important that the shop craftsman select the best method, having in mind the ease of color matching, but also considering the permanency of the results obtained.
Color in itself is a comprehensive study, inasmuch as it embraces all tints, shades, strengths and their variations. Technically, black is the absence of color and white the combination of all colors. A shade is oftentimes referred to as a color containing black, and a tint as a color containing some white. Were we to follow this rule exactly, a shade would represent such colors as olive green, plum, scarlet, etc.
Straight tints would be such colors as pink, ivory, straw, etc. However, there are many colors that contain both black and white. Hue is supposed to designate the predominating color, which would be red in a pink color. Black and white mixed together produce gray, which is known as a neutral color. Gray serves to blend or harmonize color combinations. Harmonizing color combinations are those that contain a common color. Contrasting colors contain no common color.
Black of course darkens a color and white lightens. Black tends to dull a shade, while the addition of white dilutes the tint.
Each and every color in the Opex Mixing Line has a definite purpose. It must be definitely understood that not all colors are entirely fast under all conditions, and give good coverage. All of the good properties that are essential must be obtained by the proper use of the pigments, each doing its part in certain types of blends and mixes, and if one follows the rules that are laid out in the following pages he will be nearer correct in this refinishing work than he has ever been before.
The use of these 13 base colors, with black and white, make it possible to obtain a very complete range of shades, practically all the automobile finisher will ever be called upon to manufacture. It allows the shop to operate with a minimum of colors in stock. The Opex Mixing Line are standardized colors, always attaining the same color strength, coverage, and other necessary properties. Similar results cannot be obtained by using similar colors from other manufacturers, as the tinting value will not be parallel due to the difference in the balance of pigment and binder.
We consider it highly essential that every shop develop on its staff a shader, or color mixer. Color mixing is not a difficult art to master, provided one has :
We cannot stress too strongly the following essentials to insure obtaining the best results :
Generally, it is true that the brighter and cleaner shades are not as fast to light in small quantities, when let down with white as the duller earth colors. The true test of fastness and durability of color comes when it is let down or mixed with other pigments.
A color may be relatively fast when used as a self-color, and not mixed with any other enamels, but that same color, if mixed with other enamels, and used as a tinting shade in relatively small amounts, may be quite fugitive and unsatisfactory. For example, toluidine red, known as one of the fastest of permanent colors in the color varnish industry, has obtained its reputation only because as a self color it is entirely satisfactory.
When let down with 20 parts of white the color is really relatively fugitive and not at all satisfactory. Furthermore, toluidine red-(Opex Orinoco Vermilion) bleeds in a pyroxylin lacquer vehicle. Para red (Opex Mephisto Red) has similar characteristics. Therefore, we do not recommend their use as mixing enamels. However, they do serve as very durable attractive trim colors when used straight, as is evidenced in their widespread use.
Each and every one of the Opex Mixing Enamels is non-bleeding in lacquer solvents, and can be striped over or finished over without any possibility of bleeding through.
Thus you can understand that it is highly important that the shop man should have an exact knowledge of the individual qualities and characteristics of each and every pigment which he is using, in order to obtain the best possible results in making up the color matches which he is called upon to produce.
With the thought that the consuming trade would like to know more about the goods they are using, the characteristics of the pigments that are incorporated into Opex Mixing Enamels are here given by Sherwin-Williams.
Ultramarine blue, which is one of the most permanent and beautiful of pigments, was formerly obtained exclusively from the rare and costly mineral, lapis lazuli. For many years now it has been made synthetically from clay sodium carbonate, sodium sulphate, charcoal, silica, and sulphur. Both the full and reduced shades are bright and clean, and have excellent permanence to light. The tinting or color strength is relatively low, compared to Prussian blue as is also the opacity or covering.
Prussian blue, also known as iron blue, is a synthetic pigment made from prussiate of soda, or potash, ferrous sulphate, and an oxidizing agent, such as chlorate of potash or bichromate of soda. The full shade is much deeper than that of ultramarine blue, while the tint when reduced with white pigments is a true blue and not a violet. The tinting strength and opacity are both much greater than for ultramarine. The permanence to light of full strength colors is very good, although not equal to ultramarine. In reduced shades, Prussian blue is very fugitive.
LEMON YELLOW-CHROME YELLOW
The pigments used in these enamels are light chrome yellow and medium chrome yellow respectively. They are lead chromate pigments prepared from acetate of lead and sodium bicarbonate. The medium shade is normal or 100 per cent chromate of lead, while the light shade contains approximately 25 per cent of co-precipitated lead sulphate and 75 per cent lead chromate. Both are very bright with good opacity and permanence in full shade. The reduced shades and tints, however, are quite readily affected by the action of sunlight. They do not fade out, but instead turn dark blue, due to a breaking down of the lead chromate. This tendency can be controlled to a considerable extent during the manufacture of chrome yellows. The colors used in both the lemon and chrome shades have much better resistance to light than many of the chrome yellows found on the market.
PERMANENT TONING YELLOW
The yellow which is used for this shade is an artificial iron oxide pigment prepared by precipitating ferrous sulphate with milk of lime or an alkaline hydroxide. The resultant precipitate is then dried and calcined, thus producing a synthetic pigment which approximates the natural raw siennas. The shade, however, is brighter than the earth colors and the tinting strength about three times as great. The permanence to light of both full and reduced shades is excellent.
LIGHT CHROME GREEN-DARK CHROME GREEN
Chrome greens are mixtures of chrome yellow and Prussian blue, generally put together before drying. The brightness of shade, opacity, permanence, and other properties of both pigments are thus combined. The depth of shade is determined by the ratio of blue to yellow, that is, a light shade green contains a low percentage of blue and a high percentage of yellow, while a dark shade green is high in blue and low in yellow. In order to produce a bright clean chrome green it is necessary to use a light chrome yellow since a medium chrome yellow, due to its redder shade, makes a duller or olive type of green. Inasmuch as the tints of chrome yellows and Prussian blue are not fast to light, it follows that the tints on chrome greens made from them are also fugitive. Similarly, it also follows that the full shades have relatively good permanence and cover well.
Umber is a natural brown earth color found in many localities. The pigment used in this case comes from Turkey, and is known as raw Turkey umber. Its color is due to the oxides of manganese and iron which it contains. The shade of this type of color is not especially clean, but it has some very desirable properties, in that it is especially fast to light, both full shade and as tints, and has very good opacity.
The pigment used in this enamel is an artificial inorganic color, which is a mixture of cadmium sulphide and cadmium selenide. The shade is relatively bright, and the resistance to light and weathering action is excellent. The reduced shades and tints have good permanence, but are not as fast to light as iron oxide red and sienna. The oil absorption is low, which permits the use of a high percentage of pigment, thus providing very good covering. Cadmium red is absolutely non-bleeding.
The color used here is a natural iron oxide red, containing over 90 per cent of ferric oxide. As is the case with most inorganic earth pigments, the fastness to light and opacity are excellent. The shade is especially bright for this type of pigment. It does not, however, approach the brightness of shade of cadmium red.
Siennas are natural earth colors closely related to the ochres and umbers. They differ from the ochres in that the iron oxide content is higher, running about 40 per cent as compared to 5 to 15 per cent. Like both the ochres and umbers, they are found in many locations, those from Italy being especially desirable. They are not only used in the raw state, but are calcined or heated, being then called burnt siennas. The pigment used in this case is known as Italian burnt sienna and is of this latter type. Similarly to the other earth colors, it is very fast to light, both full shade and reduced, and has good covering. It is also non-bleeding in lacquer solvents.
Chrome orange is an artificial inorganic pigment very closely related to chrome yellows, since it is a basic chromate of lead prepared from the same raw materials, namely, acetate of lead and sodium bichromate. By the use of higher temperatures and alkalies, a pigment composed of lead chromate and hydrate is obtained. The shade is especially bright and the permanence to light of the full strength and partially reduced color is very good, being even better than full strength chrome yellows. As in the case of chrome yellows, chrome orange has excellent covering power or opacity.
The pigment used in this shade is a synthetic organic dyestuff made from hydroxy naphthalene sulphonic acid. It has a bright rich shade, and is very fast to light. Its tinting strength is high and the tint very clean. Unfortunately, the reduced shades are only moderately permanent, making the color unsuitable for use in weak tints. The opacity or covering power is good, and the color is absolutely non-bleeding in lacquer solvents.
Bone black is a carbon pigment obtained from the destructive distillation of bones, that is, by heating up bones in the absence of sufficient air for complete combustion. The percentage of carbon in bone black is relatively low, amounting to only 12 to 20 per cent. Bone black is distinguished from other carbon blacks by its content of calcium phosphate. Also the shade is not as jet as lamp black or ordinary carbon black. It is, however, particularly suited as a pigment for mixing with other colors, since it is heavier in gravity, and therefore does not tend to float or separate as much as other blacks. It contains no soluble dyes and is non-bleeding in lacquer solvents. Bone black should not, however, be used straight as a body color, but only for shading.
The pigments used in auto white are titanium oxide and zinc oxide. Titanium oxide is a relatively new pigment obtained from sands which are high in titanium. This finely ground sandis dissolved in sulphuric acid, from which solution the titanium is precipitated in the form of meta-titanic acid, leaving the impurities dissolved in the solution. This meta-titanic acid is dried, calcined and finely ground to produce titanium oxide, which has greater opacity than any other white pigment. Heat and light have no action on it. Also it is not affected by acids or alkalies. The films of paints and lacquers made with titanium oxide alone are not very durable, but this property can be overcome by the introduction of other pigments.
In this case, zinc oxide has been used. This is one of the best known white pigments and has been used satisfactorily for many years. It is produced by vaporizing slabs of zinc metal in a furnace and then burning the zinc vapors by letting them come in contact with oxygen in the air. The pigment thus obtained is known as French Process zinc oxide. It has a very fine particle size and good opacity. By combining these two fine white pigments, an especially desirable blend is obtained, possessing unexcelled covering capacity and opacity