PRODUCT:
AGABÊ Test Positive Scale to control exposure, definition and resolution in thick stencils.
CHARACTERISTIC:
The Test Positive has three components:
- Gradual gray scale, divided in 10 Steps, with different optical densities.
- Straight line scale with angles varying from 0 to 90 .
- Triangular scale, starting with a width of 0,1 inch (2,54mm) and gradually decreasing to 0 in both positive and negative, divided in 10 parts.
USES:
- To define the correct exposure time (at ideal hardening of the photographic layer).
- To control the exposure (assuring the repeatability of the stencils).
- To evaluate the definition (verifying how the stencil edges are affected by the threads of a fabric).
- To measure the resolution loss (loss of details caused by light diffraction on the fabric or on the photographic layer).
Due to its small size and simple one step use, the AGABE test can be easily performed in every stencil as a quality control tool, assuring perfect repeatability.
INSTRUCTIONS:
How to determine the correct exposure time:
The exposure time is evaluated by looking at the gray scale steps remaining on the fabric after wash out.
Coat the emulsion and dry it as recommended. Place the AGABE Test Positive Scale on the stencil. The gray scale side should not be placed in contact with the screen printing emulsion. Expose the screen for an estimated time. Wash out the stencil and analyze the number of gray scale steps remaining on the stencil.
For white meshes the exposure time is correct when steps 1, 2, 3 and 4 remain on the fabric.
The stencil is under exposed (insufficient exposure) if less than 3 steps remain. This situation can reduce the stencil's resistance during printing. If more than 5 steps remain on the fabric the stencil is over exposed (excessive exposure). This can cause resolution and definition losses.
Note: When finer details are to be rendered the exposure time can be adjusted to leave only 3 steps on the fabric. If there are no fine details to be printed the exposure time can be adjusted to leave 5 steps on the fabric. This will increase the stencil's resistance.
TABLE 1: EXPOSURE LIMITS.
PRINTING IMAGE |
WHITE MESH |
Finer printing |
3 Steps |
Normal printing (recommended range) |
4 Steps |
Coarse printing |
5 Steps |
Stencil under exposed |
Less than 3 Steps |
Stencil over exposed |
More than 5 Steps |
How to adjust the exposure time:
If the number of anchored steps is out of the specified limits (incorrect exposure time), use the correction factors of the table 2. To increase the number of steps remaining on the fabric after wash out multiply the exposure time by the correction factor. To reduce the steps divide the exposure time by the correction factor.
TABLE 2: CORRECTION FACTORS.
CORRECTION FACTOR |
1 Step |
2 Steps |
3 Steps |
TO INCREASE |
Time x 1,41 |
Time x 2,0 |
Time x 2,82 |
Time ÷ 1,41 |
tempo ÷ 1,41 |
Time ÷ 2,0 |
Time ÷ 2,82 |
How to evaluate the definition:
Observe the straight line scale with a magnifier of at least 30 times and evaluate the image quality (independence of the emulsion edge from the fabric threads).
How to measure the loss of resolution:
The resolution loss is measured by the triangular scale. Each mark on the scale represents a loss of 0,01 inch (0,254mm) in resolution. Observe the triangle's vertex (thin edge). The mark on the triangle edge equals to the smallest printable detail.
ADDITIONAL INFORMATION:
This information is based on our best current knowledge. This product is solely intended for industrial use. No warranties are made or implied. Agabê will not be held liable for claims related to any party's use or reliance on information or recommendations contained herein.