What is a desiccant - description, manufacturing method and features

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

The time it takes for a layer of paint to dry, for example when painting a portrait, depends on heat, light and type of oil. There are special catalytic components that, when added to the oil, speed up the drying time. They are called dryers or desiccant, what is it? This is the name of special substances, which include s alts of various metals - cob alt, lead, manganese. Such dryers are widely used in the production of varnishes and paints for faster hardening. The proportions of substances to be added to the paint depend on its type.

A bit of history

What are desiccants? The dryers are the catalysts (monocarboxylic acid soaps) needed to form a film of materials. Their use dates back over four thousand years. In those distant times, natural materials based on manganese, lead and iron were used. Later, in the fourteenth century, copper sulfate began to be used, and already in the sixteenth - zinc compounds, in the nineteenth - basiclead and cob alt-based substances became the desiccant. In the twenties of the last century, it was possible to standardize the presence of metals in the dryer and make them convenient to use.

Composition

What is a desiccant - an additive that is added to the coating composition to speed up drying. It acts as a catalyst, speeding up chemical reactions. The composition of the desiccant may include various metals. And if there are two of them, then the drying process proceeds even faster. It is quite possible to pick up any composition of the dryer. For example, if pure oil dries out within one hundred and twenty hours, then the introduction to it:

• manganese reduces this process to twelve;
• lead - up to twenty-six;
• manganese and lead - up to seven;
• if calcium is added to manganese and lead, the time will be reduced to six.

In practice, mixtures of several metals are most often used. They are divided into:

• primary - cob alt, iron, cerium, manganese, vanadium;
• secondary - zirconium, lead, barium, bismuth, strontium, aluminum;
• auxiliary - potassium, zinc, calcium, lithium.

Use in painting

Driers for artistic paints, especially oil paints, are considered an important component that speeds up the drying process. Which usually lasts a long period. The use of dryers reduces the initial drying time of oil paint from five to twelve days to one to two days. However, excessive use of them contributes to premature aging, cracks appear on the canvas andbumps. Most often in painting they use dryers containing:

• heavy metal oxides – zinc, lead, cob alt, manganese;
• metal s alts of unsaturated fatty acids;

White lead, which is a pigment, contains a heavy metal and also has desiccant properties. Craftsmen use various mixtures of metal-based dryers. The meaning of the word "desiccant" means drying, that is, these are substances that accelerate the drying, film formation of paint and varnish coatings.

Different types of dryers used in decorative art

For ease of work with varnishes and oil paints, several types of driers have been developed:

1. Aerosol - if you need a quick drying of the picture, and it was written without mixing the dryer with paint, then you can use a spray that not only increases the drying speed, but also protects the paint layer from ultraviolet radiation. Thanks to this effect, the optical effect of painting is preserved for a long period. Aerosol desiccant can be used at all stages of work, it mixes well with oil paints.
2. Liquid - they are used to improve the drying of oil paint. They are added to the paint on the palette. At all stages of work, they contribute to the rapid drying of the paint layer and enhance the fluidity of the paint.
3. Gel-like - do not affect the viscosity of the paint, interfere evenly. With their help, dense work is dried faster.

Featuresapplications

What is this? Desiccant or dryer is a substance, the introduction of which allows manufacturers to diversify the recipe and prepare it for different areas of use. It is added to paints and varnishes in order to speed up the drying process. In practice, it has been proven that the reduction in the time required for drying directly depends on the amount of desiccant added, that is, there is a certain limit beyond which it is not recommended to add a dryer, as the drying process will slow down.

The amount of desiccant to be injected is indicated in the instructions or on the label. Used dryers are conditionally divided into the following groups:

1. Easily soluble - they are introduced into the composition when heated to 150 degrees. Among them are s alts of resin and fatty acids.
2. Sparingly soluble - for better dissolution, they require heating up to 250 degrees. These include lead acetate, red lead, pyrolusite, cob alt acetate.
3. Liquid - easily soluble in turpentine, oil and other solvents, 20 degrees is enough for them.

Most common dryers

What is a desiccant and where can I get it? These are metal compounds (catalysts) that, when added to oils, promote rapid drying. You can buy them in stores or cook at home. Most requested:

1. Cob alt - refers to the main and most used, including at room temperature. The disadvantage is poor quality deepfilm formation, formation of irregularities. Therefore, to create a homogeneous film, it is used in conjunction with other metals, such as lead, calcium, magnesium.



2. Lead - has low activity, therefore it is used together with other driers - manganese or cob alt. Accelerates the process of film formation over the entire thickness of the coating layer. The downside is high toxicity, poor compatibility with aluminum pigments, limited solubility.
3. Manganese - compared to cob alt, it is less effective for atmospheric drying materials. For thermoset coatings, as well as film forming at low temperatures, gives excellent results. At high humidity, unevenness does not form. Among the shortcomings, a rich shade should be noted, which changes the color of the coating.
4. Zirconium - it is called a substitute for lead driers. Compared with other auxiliary dryers, it has good durability, low color and yellowing.
5. Calcium - works best when interacting with active desiccants, such as cob alt.
6. Zinc - stabilizes other desiccants, increases gloss, color stability, hardness. A large introduction of this dryer into the material is allowed, since. it has low color.

Homemade

What is a desiccant - auxiliary compounds that accelerate the drying process when added to oil paints. It is possible to cook them yourself. Forthis:

1. Take a porcelain (metal) canister.
2. Put 50 grams of rosin in it.
3. Melt at 250 degrees.
4. Stir occasionally.
5. After complete melting, add a little quicklime.
6. Stir.
7. Heating is stopped after obtaining a homogeneous transparent mixture.

Industrial production

There are several ways to make driers in industry:

1. Precipitation method or wet - allows you to produce precipitated substances of better quality. As a result, they have been widely used. Currently, this method is mainly used for the manufacture of dryers. It is based on the exchange reaction that takes place in an aqueous solution between an alkaline soap and a metal s alt, it does not need to be heated to a high temperature.



2. Dry - with its help, melted dryers are obtained. Metal oxides are introduced into rosin, oil and various acids. Soaps (metal s alts) are formed at high temperatures. Among the disadvantages of this method are noted: decomposition of organic (basic) substances, as a result of which color is lost; high risk of fire.

Disadvantages and advantages of catalysts

Compounds of zinc, lead, cob alt, manganese, added to oils to speed up their drying - that's what a desiccant is.

All kinds of dryers contribute:

• darkening;
• loss of oil film elasticity;
• rapid agingpainting.

Therefore, they are added only when necessary.

In paints that dry very slowly, the dryer is added at the factory and is not required later.

Today, more and more people are working with ready-made combinations of dryers based on different metals. They have a small amount of solvents and an optimal composition of metals. The efficiency of such complexes is much higher. Benefits to note:

• global in use;
• compatibility with different solvents;
• suitable for all weather conditions.

Driers for making drying oil

Let's make it clear right away that this is the basis of oil paint. Natural drying oil is made on vegetable oils - hemp, linseed, sunflower and others. Some of them dry in the air, while others - partially. However, even drying oils are capable of reacting with oxygen and this reaction is very slow. As a result, you have to wait a long time for the paint to dry. To speed up the process, a catalyst is added to it. Thus, ordinary drying oil is nothing more than a mixture of oil and desiccant.

Many dryers are s alts of organic acids and it is really possible to cook them yourself. In a metal or porcelain container, heat fifty grams of rosin. Further, in small parts, stirring constantly, introduce five grams of calcium oxide into the molten liquid. As a result of the transformations, calcium resinate will be obtained. If atake fifteen grams of lead oxide, previously ground with linseed oil, and add in small batches to liquid colophon resin, then lead resinate will come out. Using potassium permanganate and sodium sulfite, manganese oxide can be obtained.

Conclusion

Driers are substances that accelerate the drying of materials such as enamels, oil paints, varnishes, primers, drying oils. The most efficient are dryers based on cob alt s alts, thanks to which the drying of all layers of paint is carried out evenly. They are added to paint or applied in a thin layer to wet work. The desiccant, as it were, burns out the oil base of the paint and speeds up the drying process. The advantage of cob alt dryers is that they do not impair the intensity and richness of the paint, and do not affect the color pigment.