All photopolymer signs require a top coat to be applied.
Painting NovAcryl – Many photopolymer signs are surface painted using a variety of custom colors. Signs that are decorated sub surface with paint, digital graphics and materials that incorporate color or patterns in the base substrate all require a clear coat to applied over the photopolymer. This adds the same level of protection as the paint and should be applied accordingly.
According to Matthews Paint Company, it is specified that clear coats and/or paints should have the same amount of coating (4 mil wet/2mil dry).
It should be noted that when using clear coats, the product chosen needs to have a high level of UV protection, needs to be mixed properly and be applied to the manufacturers recommendations.
Recommended painting procedures for NovAcryl photopolymers
When coating NovAcryl or Nova Polymers, with MATTHEWS ACRYLIC POLYURETHANE, the first step is to clean the polymer. It must be free of any dirt, grease, etc… You may use any of our reducers or isopropyl alcohol
When using MATTHEWS ACRYLIC POLYURETHANE, make sure the surface is clean. Apply one coat of 74-777 TIE BOND and allow to tack up approximately 20 minutes at 70 degrees Fahrenheit. Then topcoat with MAP. It is NOT neccessary to use TIE BOND for good adhesion.
When using VOC compliant MAP, our compliant coating for air regulations, be sure he photopolymer is clean. Then apply our VOC compliant material directly to the PHOTOPOLYMER. No TIE BOND is necessary for good adhesion.
Top coating of MAP and VOC MAP should be done within 72 HOURS. After 72 HOURS. After 72 hours a light scuff sanding with 400 grit sandpaper is required for good adhesion of any top coating.
Complete Matthews Paint Company Substrate Guide
Substrate Preparation Recommendations
Step #1 – Matthews is for Professional Use Only.
Step #2 – Always follow proper safety precautions when using Matthews’s products.
Safe usage requires reading, understanding, and following all label, SDS, and other product literature before use.
Step #3 – The spray area and substrate must be warm and have adequate airflow.
Application of primers, topcoats, and clear coats should never take place in temperatures under 60F/16C. Substrates should also be brought to or above this temperature guideline before applying any primer or topcoat.
Step #4 – Properly clean substrate.
Professionals don’t even think about priming or painting over any substrate that hasn’t been properly cleaned and prepared. Use proper cleaning products and procedures.
Step #5 – Use the right primer for every specific substrate.
Always use the appropriate primer and application techniques suggested from the Matthews substrate guide.
Step #6 – “When in doubt, test it out.”
Recommend testing first, the process for any new product, primer, or first time application procedures before permanent production begins. Remember that the change of seasons effect the temperature and humidity during application so periodic testing on application and adhesion confirm the product and production performance.
Step #7 – Choose the proper reducer for each application.
Review product data sheet for reducer temperature guidance.
Step #8 – Allow specific time between coats.
For both primers, topcoats, and clears, extend flash times between each coat application.
Step #9 – Adjust spray equipment.
Perform a spray pattern check prior to painting. Adjust flow, pressure, and tip if necessary. Use in well-ventilated facilities and with proper safety equipment.
Step #10 – Contact Matthews Paint Company with any questions.
Matthews’s customer service and technical assistance are both available for any color formula match, specification, or technical question that may arise.
For more complete information on all MPC solutions, you can click here
When applying paint to sub or 2nd surface clear Novacryl, you must clearcoat the first surface to protect the photopolymer. Follow cleaning procedures.
- Clean with 6428SP Plastic Prep or 6405SP Low VOC Cleaner.
- Can use 6428SP Plastic Prep as an anti-static agent by applying a mist coat and allowing to dry.
- Apply 1 medium wet topcoat.
- Allow 10-15 minutes to flash.
- Apply 2nd medium wet topcoat.
How do I use a wet film thickness (WFT) gauge?
A wet film thickness gauge is designed to give the spray operator immediate feedback as to the film build just sprayed. In most cases, measuring the dry film thickness (DFT) provides little information as it is usually measured a considerable amount of time after the actual spraying. Many things could have influenced the DFT: operator fatigue, ambient air temperature, coating temperature, etc.
There are several types of WFT gauges available. The most common being the notch gauge (see figure 1). Others types including the eccentric disk, the rolling notch gauge and the 6 sided gauges are available from specialty vendors.
Figure 1 – There are several issues that must be addressed when using a WFT gauge.
- Reading with clear coats
- Creating surface defects
When placing the gauge on a freshly painted part, the gauge must be placed 90 degrees to the part. The operator also needs to be aware of variation of the surface that may influence the reading. For example, if the surface is not perfectly flat, one direction may give a more accurate reading than another.
To use the WFT gauge, place the gauge directly on the wet finished part (see figure 2) and as described above. The notches will indicate the measured film thickness. For example, if the 1 and 2 mil notches are wet and the 3 and 4 notches are dry, then the measured thickness is between 2 and 3 mils (.002 to .003 inches).
Figure 2 – Timing
The solvent in a coating will immediately start to evaporate after spraying. In order to achieve a common method of reading the coating thickness, a time frame will need to be established. Typically, one might measure the thickness 5 to 10 seconds after spraying. If another operator measures the thickness after 20 seconds, the results would be different even if the initial thickness was identical.
Reading with Clear Coats
A clear coating on a WFT gauge would be very difficult to read. The most common method of reading clear coats is to use the gauge as a stamp on a piece of absorbent (non-gloss) paper. Many companies use the stamp method as a way of documenting the WFT.
Creating Surface Defects
After using a WFT gauge to check the film thickness, the material may not flow to hide the area where the gauge was used. If this creates an undesirable defect, place a small sample of the material in line with the operators normal spray path. This sample should be sprayed along with the part. The sample then may be checked for WFT and DFT (after curing).