Tablet Restoration & Stencil Making Part 3: Part one of this series covered a technique for creating high quality artwork for a painted clock tablet. Part two covered a technique for transferring the background and fine-line detail of the artwork onto the glass by creating a full sized decal. The clear cells defined by this background can then be filled with appropriate color to complete the tablet design.

The presentation provided here will show a second technique for getting the image onto glass. The difference however is that the technique presented here shows how to produce a very accurate silk screen and use it to apply the background paint and detail lines. This technique, while more complex than the decal method,  produces a finished tablet that is very close to the original in terms of production method and materials

Making a silk screen using traditional methods is a relatively complex process involving building a "screen" over which the silk is stretched and attached. The silk must then be treated with a special emulsion to become light sensitive. It is then exposed to light to transfer the image from a "mask" to the screen. Finally, the screen must be cleared of unneeded emulsion to create areas where paint can penetrate and areas where it is blocked. Obviously, for the occasional user, this is both a complex and fairly expensive process.

Fortunately, there are now high-tech silk screen materials that are pre-treated with the light sensitive material and are ready for exposure and use. One such produce is called  PhotoEZ . It is available directly from the manufacturer.

While new materials make creating a high quality silk screen easier than ever before, they are precise products that  require that the instructions be followed carefully. This presentation will cover the steps to creating a silk screen using the PhotoEZ product. The silkscreen is then used to transfer the image to the tablet glass.
 

MATERIAL SELECTION: PhotoEZ silk screen material is available in two grades: Standard and Hi-Resolution. Standard has 110 threads per inch while Hi-Resolution has 200. It's tempting to go immediately to the Hi-Res for the greater image clarity, but that could be a mistake.

Good silk-screening is about getting paint through the screen. It will be more difficult to get paint through 200 threads per inch than 110. As a result, getting good (opaque) coverage on clear glass can be a challenge with Hi-Res unless using special screen printing ink.

Standard PhotoEZ provides plenty of image resolution for all but the most detailed designs. It should be adequate for almost all clock tablet jobs. You will find it much easier to get good coverage with Standard than with Hi-Res so, unless the job requires it, stick with the Standard grade.
 

Screen printing involves learning several new skills and working with new materials. It is recommended that a relatively small project be undertaken until you become familiar with the techniques. This saves material and allows you to complete a number of practice pieces quickly.

Making a screen of just a portion of your project tablet image is a good way to master the specific techniques needed for the job at hand. Here, a screen of just 1/4 of the total tablet has been created for test and practice purposes.

Creating a number of sample pieces on scrap glass is a good starting point. Working with these, it is possible to determine the correct angle for using the squeegee, the correct consistency of the paint and other important variables before beginning the actual tablet.
 

MAKING THE SCREEN: In order to make a silk screen stencil, a "mask" is needed that will block light from passing through in some areas and allow it to pass through freely in others.

The easiest way to make a high quality mask is to use the original artwork produced in Part-one of this series to make a transparency.

Clear transparency material that works with a regular copier is available from most office suppliers or if you only need a single transparency, you can get it at a quick-copy store such a Kinkos.
 

The completed transparency is a full sized copy of the original artwork. The black areas will be the part of the silk screen that allows paint to pass through. The clear cells on the transparency will be solid areas on the screen to block paint. The solid areas also provide attachment of the silk screen to the glass.

If you look at the transparency with the above in mind, it will become obvious that there will be no solid areas around the outer perimeter of the silk screen and therefore no attachment points around the border. This will not work well.

To provide an attachment strip around the outer border of the silk screen, approximately 1/4" is trimmed off all four sides. This means that when the mask is placed on the silk screen material, light will hit this 1/4" border (like it does the clear cells) and a solid border strip will be created.
 

Next, an exposure fixture that will hold the mask firmly against silk screen material while it is exposed to light is needed.

The simplest fixture is two pieces of clear glass with a tape hinge holding them together. Obviously the glass needs to be large enough to hold your silk screen project. Normally, two pieces of glass 10 x 12" works our well.

Place a piece of black card stock on the bottom glass to prevent light exposure from the bottom.

PhotoEZ silk screen material is a very precise, high-tech product. Detailed instructions are provided with each order. Study these instructions and follow them closely to produce a high quality silk screen.

Working in a dim room, remove a piece of the light sensitive PhotoEZ material from its black package. Use a ruler and scissors to trim the piece to the same size as your tablet glass.

The silk screen material has a thin plastic sheet attached to it that must be removed before exposure. Use a finger nail to lift and remove this sheet from the green silk screen material.

Place the silk screen material on the black paper of the exposure fixture with the shiny side (the side you removed the thin plastic from) facing up.

Position the transparency onto the silk screen material making sure it is centered so there is a green border showing on all sides.

Carefully close the top glass onto the mask/silk screen sandwich.
 

Place a thick towel over the glass to prevent light exposure when you leave the dim room.
 

Exposure of the silk screen is best accomplished using bright sunlight (high-noon). A watch with a second hand is needed to do a precise exposure.

Place the exposure fixture on a sturdy platform in a shade-free area then remove the towel.

Time the exposure. Normally, in strong sunlight, exposure takes about 30 seconds. Do not over expose or light may seep through the masked areas making it more difficult to remove the emulsion in these areas. Follow the directions that come with the material...

When the exposure time is up, quickly re-cover the fixture with the towel and immediately remove from direct sun light.
 

To process the exposed silk screen, it is placed in a dish of cool water for approximately 10 minutes.

Notice that the areas exposed to light are noticeably darker than unexposed areas. This is one way to tell that the exposure has been successful.
 

Once the silk screen has soaked for about 10 minutes, the green emulsion on the unexposed areas of the screen will soften. Carefully lift the screen and turn it so that the emulsion side is now facing downward.

Use a soft brush to remove the green emulsion from the screen. Brush only on the side of the screen opposite the emulsion (i.e. the side now facing up). This will prevent accidentally lifting any of the emulsion from the masked areas.

Brush gently and rinse the silk screen often. As the emulsion is brushed away, only the white woven material will remain in the areas that were unexposed. The woven material will allow paint to pass through while the areas which still hold emulsion will prevent paint from passing.

Inspect the screen very carefully to ensure that all of the unneeded emulsion has been brushed away then rinse one final time.

When satisfied that the screen has been completely cleared, place it back in the sun with the emulsion side facing up. Expose it for a minimum of ten  minutes to harden the remaining emulsion.
 

The silk screen is now completed. It is a highly detailed stencil that can be used many times. Place it in a safe place until needed.

ATTACHING THE SCREEN: To use the screen, it must be firmly attached to the glass before paint is applied. To ensure a good seal, it is important that the tablet glass be clean and free of finger prints.

Carefully clean the tablet glass with Bon Ami and water. Make sure both sides of the glass are free of dirt, oil and other contamination.
 

Just prior to applying the silk screen, wipe the clean, dry glass with acetone and a clean towel.
 

A good seal between the glass and screen is essential for a sharp image. One approach recommended by the screen maker is to dampen the screen, place it on the glass emulsion side down. Smooth the screen against the glass with a finger or squeegee and allow to dry.

The green emulsion layer becomes slightly tacky as it dries which helps it to adhere to the glass. This is the preferred method since there is no chance of accidently clogging the tightly woven screen material thus preventing paint from passing through.

If you encounter bleed-over when using the screen dampening method, you can use a Repositional Stencil Adhesive to achieve a stronger seal. This is a special adhesive available from a number of sources including Lowe's home  stores.

It should be used very sparingly to avoid clogging the screen. Hold it approximately one foot above the screen and lightly mist the screen. Allow to dry for at least two minutes before applying to the glass.

With the screen correctly positioned on the glass slowly go over every inch of the screen using a finger to press it down against the glass. Pay particular attention to areas where there is fine-line detail. These are the areas where bleed-over most commonly occurs.
 

SCREEN PRINTING INKS & PAINTS: Glass, being non-porous, is more difficult to successfully screen than items such as T-shirts. On glass the paint or ink must be thin enough to pass through the screen but thick enough to avoid bleeding under the screen causing a fuzzy image. Frankly, it takes a bit of practice to sort out the best paint and the best technique.

There are several produces available for painting onto glass, but these don't necessarily work well for screening.

Pebeo Vitrea 150 Acrylic paint is made for use on glass and ceramic surfaces. This paint tends to be thin which is fine for brush work, but sometimes leads to bleeding when used on a screen. Also, Pebeo 150 black is only available in a transparent (non-opaque) form.

PermEnamel Airdry Paint by Delta, available from Michaels Arts & Crafts, is a product made specifically for use on glass. It is thicker than Pebeo but may still be somewhat thin for squeegee work. If the screen is well attached to the glass PermEnamel may work well for you.

Naz-Dar 59-000 Series Gloss Enamel from DickBlick.com is a special silk screening ink that is designed for use on hard surfaces such as glass. Unfortunately, it is fairly expensive at around $20.00 per quart and requires the use of a special solvents for clean up. If you are doing only a few tablets per year, the cost is prohibitive.

Artist's Acrylic paint, in the thick, creamy form, is personal favorite. Readily available brands include Liquitex high viscosity acrylic and Academy acrylics by Grumbacher. Both are available from art and crafts stores such as Michaels. These work well when thinned slightly with acrylic medium. Additionally, the screens can be cleaned up with just soap and water.

Water based Acrylic offers a valuable advantage when working on clock tablets. The clear cells will usually be painted with oil-based paints (metallic or solid colors). If the black background and fine-line detail had been created using an oil based paint  then the oil-based color coat would likely soften the background paint creating a bleeding problem. Fully cured acrylic will not be affected by application of an oil based paint over it.
 

There are many techniques for pushing the paint through the screen and onto the glass. The most common method is to spread a line of paint along one edge of the screen then use a plastic "squeegee" to pull a line across the screen pushing paint downward through the screen.
 

With the screen aligned and attached to the glass, a line of paint is spread across one end of the screen. As noted previously, when using artist's acrylics thinning with about 1/3 acrylic medium usually improves the coverage. Mix in a plastic cup then spread with a spoon or flat stick.

Use the squeegee to draw the line of paint  across the screen in a slow, smooth motion. It is not necessary to apply heavy downward pressure on the squeegee.

When screening on to glass, the technique used with the squeegee is very important. The squeegee should be held at an angle of around 45~60 degrees from the glass. A steeper or more shallow angle tends to force paint under the screen and cause bleeding.

Complete the pass from one side of the screen to the other. Turn the squeegee around and complete a pass back across the screen. Continue to apply light, even pressure and move slowly.

Avoid the tendency to sweep the squeegee back and forth in a paint-brush motion. This will push paint under the screen.

Make a third and final pass from one side of the screen to the other then set the squeegee aside. It will likely have quite a bit of paint on it.

Carefully lift a corner of the screen and gently peel the screen from the glass.
 

If everything went well, the image will have been transferred to the glass in crisp, bold lines. Set it aside to dry for several hours.
 

Inspect the dried screen carefully to ensure that coverage is complete. It is common to find some areas where the paint was lifted when the stencil was take away. These tiny "holidays" can be filled using a small brush.

Also inspect all of the fine-line detail. If there is any drop-out,  use an artist's brush to touch up.
 

With the black background pattern in place, color can now be added in the clear cells.

Once the color is added, an additional layer of backing will be added. This will make the black background more opaque as well as provide protection to the fill colors.

Part four of this series covers adding color and backing.

Click the link to proceed directly to Part-four
 

Silk screening is a very accurate method to get a painted image onto a tablet glass. This technique produces a finished tablet that is quite close to the original. It is a very useful approach for us "non-artist" to get a highly detailed tablet image accurately transferred to a tablet glass. With the image background as a guide, it becomes much easier to complete the tablet whether a colorful design or a basic gold and black design.

The new materials available for creating a finished silk screen are fairly easy to use and produce very fine detail. The results possible can be very impressive. It's worth giving it a try just to see what is possible.

Regards,
Tom Temple