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Troubleshooting guide

Besides developing and manufacturing high quality products, we at Agabê work hard to help you solving all of your screen printing problems. We strive to provide fast and efficient customer support. To complement our efforts, we prepared this guide in order to help in identifying and solving the most usual screen making problems. It is divided in sections according to the process steps. It helps to identify the problems, their possible causes and ways to solve or prevent them. Keep it handy in the work area. Visit our website to read the technical manuals for each product and you will also find a lot of technical information. Our technical staff is ready to help personally if needed.

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1- Coating and drying the emulsion layer 1- Coating and drying the emulsion layer

Pinholes Pinholes

CAUSE	SOLUTION
Dirt or dust on the mesh or coater.	• Degrease the mesh with HB10 or Decaprep and rinse completely. • Keep the container of emulsion closed while not in use. • Clean the coater after use and store it protected from contaminants. • Keep the dryer clean, including its air filters and blowers. • Keep the work area clean.
Air bubbles in the emulsion (due to stirring).	• After sensitizing the emulsion, let it stand still for two hours in order to eliminate air bubbles.
Air bubbles caused by the use of a low viscosity emulsion in coarse meshes.	• Use an emulsion with higher viscosity.
Air bubbles entrapped on the mesh due to coating the emulsion too fast.	• Reduce the coating speed.

Fish eyes Fish eyes

CAUSE	SOLUTION
Mesh contaminated with grease or oils.	• Degrease the mesh with HB10 or Decaprep and rinse completely. • For meshes that are heavily contaminated, use HB54 Alkaline Paste or Decaclean HR for degreasing. • Never blow compressed air onto the wet mesh. For faster drying, use a water aspirator.

Streaks or lines on the emulsion layer Streaks or lines on the emulsion layer

CAUSE	SOLUTION
Coater with a damaged edge.	• Replace the coater. Do not try to fix the problem by sanding the surface, which creates a curved edge that will coat a layer of irregular thickness.
Condensation of moisture on the pot of emulsion.	• Slowly stir the emulsion before coating. Be careful not to generate air bubbles.

Irregular thickness Irregular thickness

CAUSE	SOLUTION
Incorrect mesh tension.	• Stretch the mesh using mechanical, pneumatic devices or roller frames, up to the levels of tension recommended by the manufacturers of the fabric.
Mesh contaminated with grease or oils.	• Degrease the mesh with HB10 or Decaprep and rinse completely. • For meshes that are heavily contaminated, use HB54 Alkaline Paste or Decaclean HR for degreasing. • Never blow compressed air onto the wet mesh. For faster drying, use a water aspirator.
The mesh was not properly dried (water residues).	• Dry the mesh completely before coating the emulsion.
Ink stains from previous printing jobs.	• Use HB54 Alkaline Paste or Decaclean HR for removing all stains on the mesh. • Replace the mesh.
Irregular coater edge.	• Use a coater with a straight edge.
Coater width is not adequate for the size of the frame.	• Use a coater long enough to cover the total width of the screen. • Do not use a smaller coater in overlapping strokes. • Avoid using a coater that is too long and hits the sides of the frame.

Particles in the emulsion Particles in the emulsion

CAUSE	SOLUTION
The emulsion was exposed to freezing temperatures.	• Store and transport the emulsion in temperatures up to 75°F (25°C). Avoid freezing conditions.
The diazo sensitizer was not fully dissolved.	• Completely dissolve the diazo powder prior to adding it to the emulsion. Use water at approximately 72°F (22°C). • If Direct Addition Diazo is used, stir well to assure that it is fully dissolved prior to use the emulsion.

2- Exposure and washing out 2- Exposure and washing out

The emulsion is sticking to the positive or to the glass of the vacum frame The emulsion is sticking to the positive or to the glass of the vacum frame

CAUSE	SOLUTION
Insufficient drying time. High relative humidity in the workplace. Inefficient dryer.	• Dry the emulsion completely. The drying time is a function of the mesh count, type of emulsion and thickness of the emulsion layer. • The stencil dryer should have the following characteristics: feeding with clean and dry air and exhaustion of the saturated air (moist air), preferably to the outside of the working area. • In humid climates, use an air dehumidifier.
Certain emulsions containing photopolymers (dual cure and pre-sensitized) remain slightly tacky until they are exposed to UV light.	• Rub some starch or baby powder on the emulsion surface before placing the screen in the exposure unit.

During wash-out the stencil is peeling off or pinholes are observed During wash-out the stencil is peeling off or pinholes are observed

CAUSE	SOLUTION
Improper mesh degreasing.	• Degrease the mesh with HB10 or Decaprep and rinse completely. • For meshes that are heavily contaminated, use HB54 Alkaline Paste or Decaclean HR for degreasing. • Never blow compressed air onto the wet mesh. For faster drying, use a water aspirator.
Underexposure.	• Determine the ideal exposure time that will provide complete hardening of the emulsion layer. • Use the Agabê Test Positive to figure out the correct time and to control the exposure. • Check the lifetime of the light bulb. • Protect the electric installation against voltage variations.
The diazo was stored under excessive temperature or for a time longer than its shelf life.	• Do not store the diazo over 72°F (22°C). If stored in a freezer, the shelf life of diazo is 18 months. In other conditions, the shelf life decreases as the temperature and humidity increase.
The sensitized diazo emulsion or coated screen was stored for a long period of time.	• Diazo sensitized emulsions can be used for up to 3 months, if stored at 72°F (22°C); coated screens can be exposed in up to 2 weeks. • Write on the label of the emulsion the date in which it was sensitized.
The diazo emulsion was dried at high temperatures, spoiling the diazo sensitizer	• Do not dry diazo emulsions over 105°F (40°C). • If necessary, install controls for the temperature of the dryer.
Inadequate light source.	• Pre-sensitized or diazo emulsions should be exposed with light sources rich in UV radiation (3760Å).
Incorrect wash-out procedure.	• Wash-out using water at ambient temperature (approximately 72°F/22°C). • Reduce the pressure of the water.
Irregular thickness of the coated layer.	• See in Step 1 of this guide (“COATING AND DRYING THE EMULSION LAYER”) the problem “Irregular Thickness”.
The positive is dirt or only partially transparent. The positive is made by mounting together several pieces of film.	• Clean the positive before exposure. • Make a new positive of better quality. • Increase the exposure time to compensate for the partial transparency of certain substrates (vellum, inkjet films, etc).
Incorrect sensitizing.	• Make sure that the sensitizer is fully mixed in the emulsion. • For diazo emulsions, dissolve the powder in water (72°F / 22°C) before adding it to the emulsion. Use up all the diazo provided and sensitize a full container of emulsion. • For dichromate emulsions, sensitize only the amount to be used in up to 4 days. • Use the correct proportion of sensitizer and emulsion.
The emulsion was not fully dried before exposure.	• Dry the emulsion completely before exposure. • For thick layers (over 800 μm), dry overnight at ambient temperature. • If necessary use a dehumidifier.
Dust or dirt on the positive, vacuum frame glass or on the stencil surface.	• Clean the positive and vacuum frame glass before exposure. • Keep the dryer clean (including air filters and fan). • Keep the work area clean.

The image is difficult to wash-out (or does not wash-out at all) The image is difficult to wash-out (or does not wash-out at all)

CAUSE	SOLUTION
Over exposure.	• Determine the ideal exposure time. • Use the Agabê Test Positive to figure out the correct time and to control the exposure.
The stencil was incidentally exposed to UV light.	• Use yellow light in the areas where the screens will be handled (from coating to washing out). • Block incoming external light and incidental radiation from the exposure unit.
The positive (or masking film) does not completely block the light.	• In the case of retouched films, use OPAK, which provides an optical density of 4.0. • Check the quality of the positive: if necessary, provide a new one. • In case of laser printed positives, use OPAK LASER Image Darkener to increase the opacity. • Whenever needed, use a masking film that fully blocks UV light.
A dichromate sensitized emulsion was exposed to excessive heat after coating onto the mesh.	• Do not dry the stencil over 104°F (40°C). • Control the temperature in the drying equipment.
For dichromate sensitized emulsions, too much time has elapsed between coating and exposure or washing out.	• When using dichromate sensitized emulsions, expose and wash out immediately after drying.
Imperfect contact between the positive and the emulsion layer.	• Use a vacuum frame to provide a perfect contact between the positive and the emulsion layer.
White mesh causing light diffraction.	• Use yellow mesh. • For fine details, check out on step 3 “FINAL STENCIL EVALUATION”, the problem “low resolution (loss of fine details)”.
The light source is too close to the stencil.	• The distance between the stencil and the light source should be at least the diagonal of the coated area.

3- Final stencil evaluation 3- Final stencil evaluation

Low resolution (loss of fine details) Low resolution (loss of fine details)

CAUSE	SOLUTION
The emulsion is not recommended for fine details.	• Check the properties of the AGABÊ emulsions when selecting the ideal emulsion for a printing job. • Whenever possible, select an emulsion from the UNIFILM or DUALFILM ranges, which provide superior resolution.
Imperfect contact between the positive and the emulsion layer.	• Use a vacuum frame to provide a perfect contact between the positive and the emulsion layer. • Do not use positives made of superimposed layers of film.
The positive was placed on the wrong side.	• Place the positive correctly: The photographic layer, tonner or ink on the positive should be in contact with the stencil layer.
Positive made by mounting several pieces of film.	• Prepare a new positive, without mounting superimposed pieces of film.
White mesh causing light diffraction.	• Use yellow mesh.
Wrong mesh selection (number of threads per inch or per centimeter and thread diameter).	• The smallest printable dot should be anchored on at least two threads in each direction. • Choose a thread diameter that does not block the flow of ink in the finest details. • The straight lines on the printable image should not be parallel to the threads of the mesh (stretch at angles of 10 to 20°).
The thickness of the stencil is not compatible with the image.	• Ideal stencil thickness: for halftone dots: 10% of the thickness of the mesh. Letters/lines: 25%. • Use the Agabê Test Positive to verify and control the loss of resolution.
Over exposure.	• Determine the ideal exposure time. • Use the Agabê Test Positive to figure out the correct time and to control the exposure.
The light source is too close to the stencil.	• The distance between the stencil and the light source should be at least the diagonal of the coated area.
Inadequate light source: Multiple lamps, diffuse light, etc.	• Use a sharp light source. • Ideally, the light beams should be parallel to each other and reach the stencil at a 90° angle.
Incomplete wash-out.	• Use a soft water spray on both sides of the stencil, until the image is fully visible. If necessary, use more pressure only on the print side of the stencil (external side).
Residues of soft emulsion (scum) are clogging open areas of the stencil.	• Use HB70 Exposure Enhancer (Liquid Light), which reacts with the under exposed emulsion and fixes it.

Low definition (stencil edges are not sharp) Low definition (stencil edges are not sharp)

CAUSE	SOLUTION
Low quality of the positive or artwork.	• Check the quality of the artwork, negative and positive. • Avoid images printed with low resolution output: it should be at least 1200 dpi.
The emulsion is not suitable for high definition printing.	• The Agabê emulsions provide flat stencils and sharp edges. • Check the properties of the Agabê emulsions to select the emulsion best suitable for your need.
Wrong coating procedure built up the stencil on the internal side (squeegee side).	• Correct coating procedure: Coat twice on the external side (print side) and without drying, coat several layers on the internal side (squeegee side) according to the desired thickness. • Dry the stencil horizontally, with the print side facing down. • After drying, extra coats can be applied to the external side (print side) to increase the flatness of the stencil (for lower Rz values).
The stencil layer is too thin.	• Increase the stencil thickness by coating more times on the squeegee side (internal side) prior to drying. • Choose an emulsion with higher solid content.
Irregular stencil thickness.	• See on step 1 “COATING AND DRYING THE EMSULION LAYER” the problem “irregular thickness”.
Imperfect contact between the positive and the emulsion layer.	• Use a vacuum frame to provide a perfect contact between the positive and the emulsion layer.
White mesh causing light diffraction.	• Use yellow mesh.
Inadequate exposure time.	• Determine the ideal exposure time. • Use the Agabê Test Positive to figure out the correct time and to control the exposure.

4- Printing 4- Printing

Stencil provides short print runs (image is damaged and pinholes are created during printing) Stencil provides short print runs (image is damaged and pinholes are created during printing)

CAUSE	SOLUTION
Incorrect mesh tension.	• Stretch the mesh using mechanical, pneumatic devices or roller frames, up to the levels of tension recommended by the manufacturers of the fabrics.
Mesh contaminated with grease or oils.	• Degrease the mesh with HB10 or Decaprep and rinse completely. • For meshes that are heavily contaminated, use HB54 Alkaline Paste or Decaclean HR for degreasing. • Never blow compressed air. For faster drying, use a water aspirator.
Insufficient adhesion of the emulsion to the mesh.	• Use HB12 Abrasive Paste to make the mesh threads slightly rougher, increasing the adhesion of the stencil.
Underexposure / Inadequate light source.	• Check on step 2 “EXPOSING AND WASHING OUT” the problem “During wash-out the stencil is peeling off or pinholes are observed” and the causes “Underexposure” and “Inadequate light source”.
Irregular stencil thickness.	• See on step 1 “COATING AND DRYING THE EMULSION LAYER” the problem “Irregular thickness”.
The emulsion is not compatible with the ink or cleaning solvents.	• Check the information on the ink to find out the type of solvents it contains. • Check the properties of the AGABÊ emulsions to select the ideal emulsion for that type of ink. • To increase the resistance of the stencil to water and water based products, use HB72 or HB76 Hardeners or HB74 Stencil Catalyst.
Excessive squeegee pressure.	• Adjust the pressure of the squeegee. • Check other printing variables such as ink viscosity, off contact, hardness and shape of the squeegee, mesh count, etc.

The stencil is brittle The stencil is brittle

CAUSE	SOLUTION
Low relative humidity.	• Control the relative humidity in the work area. • Wet the stencil with water prior to printing.

The ink does not flow through the open areas The ink does not flow through the open areas

CAUSE	SOLUTION
Residues of soft emulsion (scum) are clogging open areas of the stencil.	• Determine the correct exposure time. • Wash-out completely and use HB70 Exposure Enhancer (Liquid Light), which reacts with the under exposed emulsion and fixes it.
Insufficient opacity of the positive. The positive was not retouched.	• Use a positive with optical density over 3.2. • Retouch the positive with OPAK. • In case of laser printed positives, use OPAK LASER Image Darkener to increase the opacity of the toner.
Dried ink residues are blocking the flow of ink.	• Clean the stencil thoroughly using the appropriate solvent. • Do not store screens unless they are properly cleaned. • See step 5 “RECLAIMING THE STENCIL” to ensure that the mesh is completely clean.

5- Reclaiming the stencil 5- Reclaiming the stencil

The stencil layer is difficult to remove The stencil layer is difficult to remove

CAUSE	SOLUTION
Residues of dried ink create a barrier that impairs the action of stencil removers.	• Remove the ink residues using HB52 Ink Removers (in Paste, Gel, Extra or Eco) or Decasolv LM 665 and LM 781 (environmentally safe solvents).
Use of inadequate reclaiming products.	• Use HB50 Stencil Remover. • Do not use chlorine based products (bleach) that can damage the mesh.
The stencil is made with an emulsion that has a high resistance to water. The stencil is old or catalyzed (chemically hardened).	• These types of screens are difficult to reclaim. In some cases it is possible to reclaim them using HB52 Ink Remover followed by HB50 Stencil Remover. In other cases Decaclean HR can be used successfully. • Use a more concentrated version of HB50 Stencil Remover, or prepare a more concentrated solution, adding less water than indicated.
Ink catalyst reacted with the emulsion.	• See the preceding solution.
Underexposure.	• Determine the ideal exposure time. Certain emulsions are harder to reclaim when under exposed.

Ghost image Ghost image

CAUSE	SOLUTION
The threads of the mesh are entrapping ink residues creating a “haze”.	• Use Decaclean HR or a mixture of HB52 Ink Remover and HB54 Super Alkaline Paste to remove the ghost images. (Please, read the MSDS and technical information before using the products).

IF YOU HAVE ANY FURTHER PROBLEM NOT SPECIFIED IN THE TROUBLESHOOTING GUIDE, CONTACT US FOR ASSISTANCE.

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