Six Major Decisions When Using Acrylic Glazes by Allen L. Clapp
Transparent acrylic glazes allow underpaintings to be seen through one or multiple layers. The clarity of lines and brightness of colors are all affected by six major decisions:
1.
Choice of canvas weight and weave
2.
Method of diluting acrylic paint to achieve the desired consistency and intensity
3.
Type of surface tooth under each layer of glaze
4.
Choice and use of adhesive tape or film when creating hard edges or fuzzy edges
5.
Choice of starting paint and families of colors for glazes
6.
Choice of brush filament type
Choice of canvas weight and weave
Just as the colors printed on glossy paper will appear brighter than the same colors printed on plain paper, so will colored glazes painted on smooth, portrait-weight canvas appear brighter than those painted on rough, heavy-weight canvas. This is because the larger strands of the heavy-weight canvas, such as 12 oz. cotton duck, create high knobs and low valleys as they cross over one another, compared to the relatively smooth surface created by the weave of fine strands in portrait canvas, such as 7 oz. portrait canvas. Even heavier portrait canvas (such as a fine-weave 10 oz. weight) will have a smoother surface than a canvas of the same weight with a medium or coarse weave.
Surfaces with large bumps reflect light in many directions. As a result, less color is reflected to the eye of a viewer and the colors will seem subdued. This is why matt finishes make colors seem duller and gloss finishes make colors seem brighter. Similarly, the high peaks and deep valleys created by the large threads of a heavy-weight canvas as they cross each other will scatter reflected light more than the relatively lower knobs and shallower valleys of a lightweight portrait-grade canvas woven from finer threads
When a thin color glaze is applied to a course-weave canvas, the color is further subdued for a related reason. Glazes have lower viscosity than heavy-bodied or structure paints. In many cases the colored glaze will run off the peaks of the tops of the crossing threads and settle in the valleys—essentially trying to run under the crossing threads. This creates less color on the tops of the threads to be reflected to the eye. In addition, the light going to or reflecting from the color in the valleys between the threads is partially blocked by the adjacent peaks of the large threads, thus limiting the color to be reflected to the eye. The result is subdued (pale) color that looks more like thin watercolor.
In addition, adhesive tape or film will not lay down as tightly on a coarse canvas weave. Thus, it is more difficult to limit colors running under a taped stop line with a coarse canvas weave.
© 2009 Allen L. Clapp; Raleigh NC www.ClappArtStudios.com
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Six Major Decisions When Using Acrylic Glazes
See the discussion on creating hard edges below. Both types of canvas can be used effectively, depending upon the look that is desired.
When I am working only with opaque acrylics, or I want subdued colors in acrylic glazes, I use a 10-12 oz. canvas—primarily Windsor & Newton Deep Edge, Creative Mark Edge, or
Paramount Professional canvases, all of which are available from Jerry’s Artarama.
When I want to have brighter colors and sharper lines—particularly when I want to have bright, wet-in-wet color effects—I typically use the lightweight, portrait-grade YES! brand canvas. The
YES! canvas is (a) primed to accept all water media paints and (b) available from Jerry’s
Artarama in the following types.
1.
stretched canvas in a large variety of sizes—I use this for most of my work featuring acrylic glazes,
2.
several sizes of rolled canvas, which I use for larger or odd-sized paintings, and
3.
pads, which I use for experiments to see the effect of different techniques.
If brighter colors and sharper lines are desired, and the only canvas that is available in the size desired is a course weave, the valleys between threads can be filled in with gesso and sanded.
Matisse makes a low viscosity gesso that is perfect for this purpose. I typically use a brush to paint on two or three thin layers of gesso. I let it dry between coats and sand it lightly with 120-
200 grit sandpaper after each coat. A damp rag will remove the last of the sanding dust.
The Creative Mark Edge canvas is a medium weight canvas that, like the YES! Canvas, is triple primed to accept all water media. The intensity of color reflected from that canvas lies between the high intensity of the YES! canvas and the lower intensity reflections from the Windsor &
Newton Deep Edge or Paramount Professional canvases.
Method of diluting acrylic paint to achieve the desired consistency and intensity
Acrylic paints are a made with a water-based media. One of the great attributes of acrylic paints is that they polymerize when they dry and resist water from that point. Unlike watercolors, acrylic paints can be layered without affecting underneath layers.
Minor thinning with water to help lubricity of the paint or create a relatively heavy transparent glaze will not affect the ability of the paint to polymerize. However, when major thinning is desired and more than around 40-50% water is used to achieve thin, transparent glazes, the acrylic may not polymerize and it may be adversely affected by subsequent layers of glazes. The amount of water that can be used varies to some extent with manufacturer and grade of paint
(some student grades are affected more than some professional grade paints). To assure that the acrylic paint glaze can polymerize, more than 50% acrylic medium must be maintained in the glaze. I recommend not less than 60% acrylic medium, unless the mix has been tested.
Most acrylic artist paint manufacturers produce a low-viscosity medium for use in increasing the transparency and reducing the viscosity of acrylic paints. I primarily use Matisse Acrylic
Painting Medium for this purpose. Liquitex Glazing Medium and Golden GAC 100 are similar products intended to be used to dilute acrylic paints to create glazes.
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Six Major Decisions When Using Acrylic Glazes
The above low viscosity media produce a semi-gloss surface. Some manufacturers produce a gloss glazing medium that can be used to increase transparency and, in some cases, lower viscosity of the paint. However, unless only one layer of glaze is to be used, a gloss medium should be avoided because it will tend to cause streaking in the later layers. See the discussion on surface tooth below.
In many cases, the desired effect can be created by diluting the paint with only the glazing medium. In other cases, water can also be added to the mix to create the desired effect (or decrease the cost of the diluting medium).
Most low-viscosity acrylic media can be mixed with water up to about 50% water and then mixed with the paint to create the desired transparency of the glaze. The paint itself is created by suspending pigment in acrylic medium. Adding a mixture of low viscosity acrylic medium and water that has no more than 50% water to an acrylic paint keeps the resulting proportion of medium-to-water at well more than 50% medium and, thus, preserves the ability of the acrylic glaze to polymerize. Check the web site of your paint and medium manufacturer for specific limits on proportions of water in the mixture.
Most low viscosity acrylic painting mediums that are used to produce acrylic glazes leave a semi-gloss surface after they dry. As a result, the next layer of glaze may tend to bead up and produce streaks—particularly if the glaze has a high proportion of water in the mix—unless the surface tension is reduced by adding a surfactant to the glaze. I primarily use the Matisse
Surface Tension Breaker to reduce surface tension and allow the glaze to lay down smoothly to reduce streaking or beading. Liquitex Flow Aid and Golden Acrylic Flow Release are similar products.
My experiments have shown that using a recipe mixture containing 45% Matisse Acrylic
Painting Medium, 45% water, and no more than 10% Matisse Surface Tension Breaker does a good job of limiting streaks and producing bright, permanent glazes. Too much surfactant in the diluted paint mixture can cause the glaze to be sticky. Depending upon your paints, the amount of water you use in your diluting mix, and the nature of the surface under the glaze, you may find that you only need about 3% surface tension breaker to have the glaze lay down smoothly.
In practice, I carefully measure amounts of water in my desired storage bottles and mark fill lines for each of the three ingredients in the recipe. Once the bottle is marked, I never have to measure again—I just fill to the appropriate line. I always keep at least two bottles of the recipe at hand, so that I cannot run out at the wrong time. When one is empty, I wash it out and then refill to make a fresh batch.
When I make a new batch, I CHEAT! I always fill the acrylic painting medium first and go above its line. Then I add the water to exactly its line. As a result, I start out with a little more than 50% medium in the mix. Then I add the surface tension breaker to about half of its line level. My aim is to get between 3% and 5% surfactant in the overall mix. I do not want to
approach 10% surfactant, since that can make the resulting glaze sticky with some paints. I know—this adds up to a total of less than 100%. I just find it easier to think in terms of a ratio of
>50%:45%:<5% than a ratio of 50%:46%:4%, which is more like what I actually produce.
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Six Major Decisions When Using Acrylic Glazes
I usually mix this recipe with the acrylic color is a ratio of 2/3 recipe to 1/3 acrylic paint as a starting point. Experience shows that some of the lighter colors, such as a light yellow, may need a higher ratio of paint. Darker colors usually require more of the diluting recipe to achieve the desired transparency and vibrancy. Since the paint has an acrylic medium carrier, this makes the actual percentage of medium go up to or above 60% and assure polymerization.
Type of surface tooth under each layer of glaze
Just as the relative smoothness of the surface of the canvas affects the overall look of the result, the smoothness of the surface underneath succeeding layers of transparent glaze affects the result. In a perfect world, we could use gloss mediums in our glazes and add layer upon layer without adverse effects. Unfortunately that is not the case.
The glossier the surface of the underpainting, the greater will be the tendency of the next layer of glaze to bead up and streak, similar to water beads on a freshly waxed automobile. The surface tension breaker that is included in the recipe that I use to dilute the acrylic paint and create the glazing medium helps to control beading and streaking, but it may not completely prevent it when the glaze is applied over itself. To some extent, this will vary between paints of different manufacturers or even between paints of the same manufacturer.
If I want the glaze to have a beading/streaking look, I will paint the area to be covered by the glaze with a thin layer of straight Acrylic Painting Medium or Gloss Medium. The gloss medium produces even more of the effect.
However, if I want the smoothest possible layer of transparent color glaze, I will coat the entire area to be covered by the next layer of glaze with a thin layer of Matt Medium. This puts more tooth on the surface and allows the layer of glaze to lay down flatter with less or no streaking or beading.
Choice and use of adhesive tape or film when creating hard edges or fuzzy edges
Tape or adhesive film can be adhered to a painting surface to define a hard edge. Tape is typically used for straight line edges. Adhesive film is typically used where either (1) curved edges are desired or (2) areas need to be uncovered for one or more layers and covered for other layers. Although wide or overlapped sections of tape can be used to create curved edges, adhesive film is often easier to use.
If the tape or film is not perfectly adhered to the substrate, the low viscosity glaze can easily run under the tape and produce a fuzzy edge. If fuzzy edges are desired, it is best to lightly adhere the tape or film and let the paint run under it. In this case, the edge of the tape should not be sealed to the painting substrate.
If clean, sharp, hard edges are desired, adhesive tape or film can be cut to length and desired shape and applied over the underpainting to limit the flow of the next layer of paint. For a truly sharp edge, it is necessary to seal the junction of the edge between the tape or film and the exposed underpainting with a medium to limit the opportunity for the glaze to run under the tape and create a fuzzy edge. Sealing the edge is particularly critical where the tape or film cannot be immediately removed to clean up runs, because it must stay down in place for subsequent layers to be applied on one or both sides of the tape.
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Six Major Decisions When Using Acrylic Glazes
If paint runs under the tape or film, it can be removed with a damp brush if the tape or film is removed before the paint dries. See discussion of brush choice below.
Tape is best used where a straight-line edge is desired. Multiple sections of tape can be used to create the outside or inside of rectangles or other shapes with straight edges. When creating the outside of a straight-edged shape with tape, the length of each piece of tape is not critical, so long as it covers the whole length of the side. However, when creating the inside of a shape, the length of each piece is critical, to assure that it both (1) makes a sharp corner and (2) does not extend into the area to be painted.
When taping off the inside of rectangles, I often find it easier to start with a square end of a piece an inch or so longer than needed and place one end precisely at the corner. I lay the tape down along the desired line until approaching the other end. I then measure and cut the length to end about halfway through the width of the next piece. The starting end of the next piece then is precisely placed to complete the corner. As a result, the second end of the last piece overlaps the precisely placed first end of the starting piece and no lengths are really critical.
I have experimented with over 50 different tapes to create hard edges. For most applications, I have found that the White Artist’s Tape available from Jerry’s Artarama does an excellent job of
(a) laying down a clean, sharp line and (b) adhering to the underpainting well enough to limit running of structured (heavy body) acrylics without sealing. However, all tapes or films should be sealed when applying glazes and a hard edge is desired.
Adhesive tapes recommended for use on acrylic paintings.
1.
Artists’ White Tape: 1/4", 1/2”, 3/4", and 1” wide—for covering up lines of the underpainting to allow them to show through the next layer and for creating hard edges of painted sections. Works for most applications. Can also be used without sealing/burnishing to create fuzzy edges.
2.
3-M Artist Tape for Curves: 1/6 th inch wide—for leaving small lines of the underpainting showing through
3.
3-M Delicate Surface Painters Tape: blue; 1” and wider widths—for creating edges of painted sections—is particularly useful for glazes and washes to be applied over bumpy surfaces because it will follow bumps better than the Artists’ White Tape. However, it does not stick as well as the Artists’ White Tape and must be sealed to create a hard line with either structured paint or glaze.
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Six Major Decisions When Using Acrylic Glazes
4.
Watercolor Wash Out Tape: 1” and wider widths—a good substitute for 3-M Delicate
Surface Painters Tape for putting hard edges to washes and glazes.*
5.
Drafting Tape: 1/2" and 3/4" wide can be substituted for Artists’ White Tape for laying down structure/heavy body acrylics, but does not work as well for glazes that may run under the tape. Can be used without sealing where a fuzzy line is desired.
6.
3-M Painters Tape: The regular blue painters tape can be used the same as drafting tape.
Graphix Low-Tack Frisket Film can be drawn upon to allow it to be cut to shape with scissors or knife. It is particularly useful where intricate curves are desired or where sections need to be lifted and reapplied for subsequent layers. This adhesive film was designed for use with an airbrush and does not have to be sealed in that application. If the edge is burnished with hard rubbing with a fingernail, it will usually seal well enough without applying a sealing medium to create a hard edge with high-viscosity structured (heavy body) acrylics. However, the edge should be sealed when applying low-viscosity glazes.
Choice of starting paint and families of colors for glazes
There are four basic choices that must be made to select the most appropriate acrylic paint with which to create an acrylic glaze.
1.
Viscosity. The best results are achieved by starting with a low-viscosity acrylic paint.
With most manufacturers of professional artist-grade acrylic paints, the same amount of pigment will be used in both the high-viscosity, heavy bodied (structured) acrylic paint and the low- or medium-viscosity (fluid) acrylic paint. The difference is that the fluid acrylic uses a lower viscosity medium that allows the paint to flow much easier. Thus, it requires less additional low-viscosity medium to produce a glaze. Some heavy bodies acrylics have to be thinned too much to achieve the desired consistency and do not produce as luminous a glaze as the lower viscosity acrylics. Matisse Flow, Liquitex Soft
Body, and Golden Fluid Acrylics are appropriate for creating glazes.
2.
Transparency. Starting with a transparent acrylic base color will result in the most vibrant colored glaze. Next best is a semitransparent color. Opaque colors may be used to produce a glaze, but the color will not be as vibrant as a similar transparent color.
Many manufacturers make some basic earth colors in both an opaque and a transparent type.
3.
Color family. The pigment used for each paint is shown on the container. The pigments are numbered by basic color family: R—red, Y—-yellow, G—-green, Bl—blue, Bk— black, O—orange, V—violet, etc., and all pigments are preceded by a P. For example,
PG7 (phthalocyanine green) is pigment green 7. Any yellow-green or blue-green that has
PG7 as a major pigment should go well together. A blue-green or green-blue mixed from phthalocyanine blue PBl15.3 and PG7 will be an incredible color. In some cases, the same basic pigment may be used in many different colors, but the pigment is treated differently during manufacture to create different related colors. PR101 is a good example. It is used to create Red Oxide and a variety of Siennas, all of which will go together.
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Six Major Decisions When Using Acrylic Glazes
4.
Pigment particle size. Some manufacturers mill the pigments used in their low-viscosity acrylics finer than the pigment used in the high-viscosity paints. This allows the lowviscosity acrylic to be appropriately thinned and used in airbrushes. It also allows a glaze to have more vibrant color when thinned down to levels that give just a hint of color.
For my glazes, I use the Matisse Flow low-viscosity acrylics almost exclusively. The pigment has been milled down so fine that it can easily be used in even the smallest of airbrush nozzles
(some low-viscosity acrylics must be used with larger nozzles). Matisse Flow produces incredibly vibrant colors in glazes. I can dilute the color so much that the glaze looks like colored (or white) smoke. Not only is this paint extremely versatile, the color range is wide and the families of colors that have been built by Matisse to go together (such as the Australian series and the Landscape series) produce some incredible combinations of colors.
The Matisse colors that I use most often for glazes are: Australian Sienna, Australian Yellow
Green, Southern Ocean Blue, Phthalo Blue, Phthalo Green, Yellow Mid (Azo), Yellow Deep,
Matisse Red Light, Matisse Scarlet DPP, Magenta (Quinacrodone violet), Australian Red Violet,
Australian Sky Blue, and Dioxazine Purple.
Mixing colors
Do not create your glaze mixture by mixing paint and diluting medium with the brush that you will use to apply the glaze. You will usually have a glob of paint hidden somewhere in the bristles that will come out on the canvas and create streaks. Use a palette knife in an appropriate container, let the glaze sit for a few minutes and mix again to assure a complete mixture.
I mix my glazes in porcelain dishes from the Creative Mark Porcelain Palette Treasure Classic
8-Piece Sectional palette set that has six wedge-shaped dishes around a round dish in the center of the wire carrier. The wedge-shaped dishes have a pouring spout lip on one end and plenty of room to mix a batch of glaze with a palette knife. I keep one wedge dish open for mixing glazes and use the other dishes for keeping large amounts of my most-used acrylic paints. This eliminates wasted paint, because I spritz the paint with water and cover the dishes with plastic cling wrap between sessions (I have experimented and left one covered for months and it kept the paint in good shape).
Porcelain Palette Treasure Classic 8-Piece Sectional Palette Set
Storing glazes between sessions
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Six Major Decisions When Using Acrylic Glazes
I always mix more glaze than I expect to need. I pour the mixed glaze into small Rubbermaid containers made for storing pudding in lunchboxes. These have a rubber top that will seal against spills and that matches up with the bottoms of the plastic cups so that several can be stacked upon one another and be picked up as a unit. This takes up less space when traveling or when they are not in use. I tried over a dozen types of plastic containers with plastic lids. All were fine for holding full-bodied paints, but all leaked the thin glazes when tilted on the side.
Marking glaze mixtures
I have tried all kinds of color of markers. Most could not be seen when marked over a similar color. The one that works universally over all colors is the Sharpie metallic silver marker.
Choice of brush filament type
The filaments used in brushes differ in a variety of ways. Many of the natural bristles will hold more paint than man-made fibers that are comparable in feel. However, the technology used to produce fibers for brushes is changing rapidly. Some of the newer man-made fibers and combinations of fibers rival good natural bristle brushes in color holding power. In many cases, the man-made fibers will be superior to the natural bristles for creating sharp edges.
The bristles used to push around high-viscosity acrylics (and oil paints) are usually stiffer than those used for watercolors and for washes and glazes. They often will swell with paint and will not easily produce a sharp edge.
The best choices for laying down acrylic glazes are brushes intended for watercolor or other washes. They tend to hold a reasonable amount of color to allow the stroke to go all the way across the intended area and they have fine, soft bristles that tend to leave fewer streaks in the glaze. The brushes that I use the most for that purpose are the Polar Flo wash brush and the
Creative Mark Colorburst wash brush. I also use Windsor & Newton wash brushes.
For opaque acrylics, I usually use one of the ProStroke brushes. The ProStroke White Bristle brush (with the silver-tipped handle) is better for laying down areas where you want the brush strokes to show. The ProStroke Powercryl brush (with the red-tipped handle) is better for laying down smooth layers of opaque acrylics and for blending one color into another. The
Powercryl brush is very springy and produces a clean line with either opaque acrylic paints or glazes. This is the brush that I use to clean up areas where paint runs under the tape or film. The springy fibers allow me to wipe off the excess and leave a clean line at the edge of the paint or glaze.
I find these runs easy to clean up with a damp Powercryl brush. I first pull along the intended line in one direction and wipe the brush on a paper towel. Then I go back in the other direction to pick up whatever was smeared as the first pass pulled away. I usually rinse the brush every two or three strokes. The brush must be damp, but not wet. If it is wet, it will tend to make the paint along the edge run out onto the area just cleaned.
A newer, more expensive ProStroke Red Sable brush is excellent for oils and good for watercolor, casein, and acrylics. It combines some of the best attributes of the White Bristle and
Powercryl brushes.
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