Chalk ground
Chalk primer or gesso is a luminous and absorbent primer that is usually made on an acrylic basis (acrylic chalk primer ) today. Although artists' primers have adopted the traditional names, they are no longer composed of the original components. In terms of their painting properties, however, they are comparable to conventional chalk grounds. They are used in oil painting , gilding and as a primer for the colored version of carvings or plaster casts .
Traditional primer paints
The primer plays an important role in building up a coat of paint. A primer coat must never be too “greasy” because otherwise the subsequent coats - if they are kept “leaner” - will cause cracking . Finished coats should not be over-greased either, as they tend to shrink.
Glue pot or glue water: The glue pot serves to seal the absorbent surface. In principle, all animal hot glue can be used. However, compared to the higher quality rabbit glue, bone glue has the advantage that its lower gelling point allows greater penetration depth. Let 60–80 grams of granulated glue (powder or splinters) soak in 1 liter of water for 24 hours and heat to approx. 60 ° C in a water bath . The canvas should be pre-glued with glue before priming and then dry well. Acrylic binders can also be used as a substitute for glue and the chalk base can be created in this way.
Primer pigments : The primer pigments are made up of fillers and zinc white . The best filling chalk , natural plaster of paris ("Lenzin", not fired model plaster) and white marble powder are possible. Chalk gives fine, soft grounds that need a little more zinc white addition. Plaster bases are harder and the lightest. Marble powder becomes so hard and rough that the brushes wear out a lot while painting - at least during the first few jobs. It is mainly suitable for casein primers and paintings in larger formats.
Glue Chalk Krund: Part of chalk dust and part mixing zinc white in powder form and in one to two parts pure water mix is free of lumps. Then bind with a part of warm glue water. This glue-chalk base is applied crosswise with a brush at intervals of 1/4 hour and in two to three layers. In the case of large areas, a little pure water is added to the last coat so that the base does not crack. Adding 10% alum to the glue water makes the glue water-insoluble. Painting over the glue and chalk base with four to six percent formalin solution serves the same purpose. Water-thinnable paints can be used to paint on a surface prepared in this way.
Semi-oil primer, semi-chalk primer or tempera primer: When using canvas as a picture carrier , it is advisable to use a so-called semi-chalk primer (a slightly absorbent and slightly glossy primer), as the chalk base tends to crack on flexible picture carriers. Mix 1 part chalk flour and one part zinc white in powder form and stir in one part of the gelled glue potion. Then 1/4 to 1/2 part of linseed oil varnish is added dropwise, stirring constantly . Finally, the mixture is slowly diluted with a part of water ready for use. Or you mix one part each of chalk and zinc white with a cooled glue pot and carefully stir in one part of the linseed oil varnish under heat. The more linseed oil varnish is added, the less the bottom sucks. Alum or formalin are omitted here. The semi-oil primer, like the glue-chalk primer, is applied to pre-glued canvas after it has dried well. The coats are applied at intervals of about 1/2 hour when the previous coat has set. A semi-oil primer dries quickly and can be painted on the next day. The longer the dry season, the better the reason.
Oil base: The oil base contains a higher addition of linseed oil varnish. After one coat of glue potion, two thin primer coats with semi-oil primer follow, consisting of: one part chalk, one part zinc white, one part cooled glue potion and only then 1.5 to 2 parts linseed oil varnish are carefully stirred in under heat.
Stone base: If the substrate is made of wood, a stone base should be applied as the first layer, otherwise the chalk base could break out due to any resin . The primer consists of stone chalk, which results in firm and non-slip layers. At the same time, it stabilizes the substrate and, thanks to its crystalline structure, creates a good connection to the later white ground. For the production you use 3 parts stone chalk to 1.5 parts water. This mixture is left to soak overnight. The next day, the excess water is poured off. Rabbit glue is recommended as a binding agent , as bone glue becomes very brittle in high concentrations. The mixing ratio for the glue is 1 part glue to 1.5 parts water. After it has swelled overnight, the dissolved glue is obtained by heating it to 60 ° C in a water bath. This is now mixed evenly with the chalk paste and then sieved. With regard to the tendency to crack formation, the stone base must not be too thick. If necessary, you can add a thin glue pot to it. The order is carried out by dabbing with an investor (bristle brush). You should avoid dabbing one spot twice in a row, as otherwise cracks may appear in the already dried layer. The processing temperature is 50–55 ° C. The stone primer is sufficient if an even coat has been applied (usually one or two coats). The wood surface and structure should still be visible.
insulation
Isolation reduces the absorbent effect of the chalk ground. For this you use diluted and thinly applied glue potions, alcohol varnish or resin varnish.
Resin essence varnish : To do this, one part of dammar resin is dissolved in three parts of rectified turpentine , whereby the resin is hung in gauze bags in the turpentine so that any residues do not contaminate the essence varnish. This varnish is used universally. It is added to the artist's colors, especially the white colors, as a sikkate substitute . It is also needed to isolate the glue-chalk base so that it sucks little or not at all. It is important to ensure that the varnish is applied as thinly as possible. It is also used as a retouching varnish for matt spots in the picture; to do this, it must be diluted with 25% turpentine. Blind (matt) areas can also be pre-coated with a diluted dispersion binder .
Alternatives
Alternative primers such as high-quality facade paint for outdoor use or acrylic binders give particularly good results. They are much more elastic, but they don't suck. Exterior facade paint is designed for extreme weather conditions and optimally adapts to fluctuations in humidity and temperature. Acrylic binder can be colored with white pigment (color paste with water) or white acrylic paint. If undiluted, the coatings are particularly elastic and adhesive for subsequent layers. Radiator paint is a modern oil base because it is elastic and greasy. Special primers from the hardware store are only suitable for rigid picture carriers such as wood or walls.
Applying the chalk base
After the workpiece has dried, the basic application can now be carried out in three successive steps: “dabbing”, “rubbing” and “priming”. Depending on the type of processing and workpiece, different primer applications are recommended. For a smooth frame profile, dab twice, rub twice and prime twice.
With the so-called “dabbing”, the hand-warm, relatively thick chalk ground is massaged onto the workpiece with a round bristle brush and then dabbed. It is important not to apply the chalk base too thick. The stippling creates an enlarged surface, which offers a good anchorage option for the subsequent second application.
The “rubbing” follows the dabbing. The hand-warm chalk ground, diluted with glue and water, is applied with a long-haired bristle brush. The brush always remains in contact with the surface and a lively surface is created through even, wavy brushstrokes (the brushstrokes should still be recognizable), which in turn forms good connection options to the next layer of primer.
With the "Ausgrund", a chalk ground also diluted with glue and water, the third and last primer layer is created. The application is carried out with a soft, long-haired bristle or hair brush “wet on wet”. The workpiece is covered with the largest possible amount of chalk ground in the brush. On a frame you start more in the middle and then pull the ground smoothly outwards. The flow behavior can be optimized with a maximum of 5% addition of commercially available alcohol .
In summary, when building up the chalk primer, it can be stated that the base coat is thinner from layer to layer, the glue concentration is lower and the proportion of liquid is higher. The workpiece must dry well between all work steps.
grind
After the final drying, the primer is quite rough and should be sanded. This can be done wet or dry. For wet sanding, the sandpaper should have a grit of 360 and for dry sanding a grit of 220. But you can also use pumice stone . For flat surfaces, it is best to put sandpaper around a block of wood with rounded edges and sand in circles with light pressure. If the canvas is on a stretcher frame , pieces of cardboard should be pushed underneath so that the frame edges do not push through. If the desired smoothness is achieved, it is swept off thoroughly. If you have sanded off too much, you have to prime again and sand down carefully.
Individual evidence
- ↑ a b c d e f g h Which primer: Gesso, chalk primer, oil primer or facade paint? on kunst-malerei.info. Retrieved February 28, 2014.
- ↑ a b c d e Poliment gilding. to Wilhelm Wasner Blattgold GmbH. Retrieved February 28, 2014.
- ↑ a b c d e Sax - colored profile (primer). at Sax colors . Retrieved February 27, 2014.
- ↑ a b Bodo W. Jaxtheimer: artist on Sundays. Südwest Verlag, Munich 1973, ISBN 3 517 00423 5 , p. 264.
- ↑ Poliment gilding. on malerwissen.de. Retrieved February 28, 2014.
- ↑ Gilding 2: Poliment - chalk primer. on painter sheet knowledge. Retrieved February 27, 2014.