When applying road markings, thermoplastic paint is widely used for its exceptional durability, high reflectivity, and fast application speed. Recently, one of our customers reported seeing some sediment in the strainer of their road marking machine and asked whether this would affect the final marking quality.
This is one of the most common questions we receive from contractors and road authorities worldwide. At Lighten Traffic, we’ve been manufacturing high-quality thermoplastic road marking paint for over a decade, and we’re here to clear up the confusion: sediment in thermoplastic paint is usually normal and not a sign of poor quality.
Let’s take a closer look: Why does thermoplastic paint settle? And does settlement mean poor quality?
1. Where Does the Sediment Come From? Meet a Key Ingredient – Silica Sand
Thermoplastic road marking paint contains silica sand (also called quartz sand) as a primary filler, typically making up 40-45% of the total composition. This essential ingredient serves two critical purposes:
- It helps the marking bond firmly to the road surface by creating a mechanical interlock
- It significantly improves abrasion resistance and skid resistance, extending the service life of the markings
Because silica sand has a much higher density (2.65 g/cm³) than resins and pigments, some particles naturally sink to the bottom during storage or transport. This is a purely physical characteristic caused by gravity – not a sign of spoilage, contamination, or a quality defect.
Coarse Sand vs. Fine Sand: Trade-Offs
How obvious the settlement appears depends largely on the particle size of the silica sand used in the thermoplastic paint. Different formulations use different sand sizes to meet specific performance requirements:
Coarse Sand (Larger Particles)
- Advantages: Better abrasion resistance, faster drying, better flow properties
- Ideal for: High-traffic highways, busy intersections, and areas with heavy truck traffic
- Trade-off: Heavier particles settle more easily and are more visible in the strainer
Fine Sand (Smaller Particles)
- Advantages: Settles more slowly; produces a smoother surface finish
- Ideal for: Low-traffic residential streets, parking lots, and decorative markings
- Trade-off: Lower abrasion resistance, slightly slower drying, and shorter service life on heavy-duty roads
For more information about different thermoplastic paint formulations, visit our thermoplastic road marking paint product page.
2. Different Countries, Different Preferences
Road marking requirements vary significantly around the world, and these differences directly affect the thermoplastic paint formulation – including the type and size of silica sand used. That’s why a certain amount of settlement is normal across different suppliers and regions.
For example:
- Hot regions (Middle East, Southeast Asia): Demand good heat stability and resistance to rutting. Formulations often use higher softening point resins and coarser sand to prevent melting in extreme heat.
- Cold regions (Northern Europe, Russia): Focus on low-temperature flexibility to prevent cracking in freezing temperatures. Formulations include more plasticizers and may use finer sand for better flexibility.
- Developed countries (EU, USA, Australia): Specify strict anti-skid and reflectivity standards. Formulations balance sand size for both skid resistance and durability, often complying with standards like AASHTO M249 or EN 1871.
At Lighten Traffic, we offer custom thermoplastic paint formulations tailored to your specific climate and regulatory requirements. We also provide a complete range of road marking equipment to ensure optimal application results.
3. A Little Settlement Won’t Hurt Performance – Just Do These Two Things Before Application
If you see a small amount of sediment in the strainer of your road marking machine, there is no need to worry. As long as you take the following two simple steps during melting, the final marking quality will be just fine:
â‘ Stir Thoroughly
After loading the thermoplastic paint into the melting kettle, mix it for a few extra minutes to evenly re-disperse the resin, pigment, and silica sand. Do not start marking immediately after melting.
- For best results, use a mechanical stirrer rather than manual stirring
- Stir continuously while heating to prevent localized overheating
- Scrape the bottom and sides of the kettle to ensure all settled particles are re-suspended
â‘¡ Control the Temperature
The standard thermoplastic paint application temperature is 180°C – 220°C (356°F – 428°F). Always check the manufacturer’s specific recommendation for your product.
- Overheating (above 230°C) ages the resin, causes discoloration, and can lead to premature cracking
- Too low temperature (below 170°C) reduces flow, prevents proper adhesion, and keeps sand particles from staying suspended
- Maintain a consistent temperature throughout the application process
Done correctly, minor sedimentation does not affect adhesion, abrasion resistance, reflectivity, or service life. For more detailed application instructions, download our road marking application guide.
Bottom Line: Sedimentation ≠Bad Quality. Proper Application Is What Matters.
Let’s recap what we’ve learned:
- Sediment in thermoplastic paint mainly comes from silica sand – it’s a normal physical phenomenon, not a quality defect
- Coarse sand settles more, but its superior wear resistance and fast drying are invaluable for high-traffic roads
- Different climates and local standards lead to different formulations; the amount of settlement alone is not a reliable quality indicator
- Stir well + control temperature – a little sediment will not harm your line marking
When to Be Concerned
While minor sediment is normal, there are a few signs that may indicate a genuine quality issue with your thermoplastic road marking paint:
- Large, hard clumps that cannot be broken up with stirring
- A strong, acrid smell when melting (indicates degraded resin)
- Significant discoloration or uneven color after mixing
- Poor flow even at the correct temperature
If you experience any of these issues, contact your supplier immediately.
Need More Help?
If you face other road-marking challenges (clogged machines, line peeling, poor reflectivity, etc.), feel free to reach out. We are a professional manufacturer of thermoplastic paints and marking equipment, offering full support from product selection to application techniques.
We also offer a complete range of complementary road marking products, including road marking glass beads for enhanced reflectivity and cold paint road marking solutions for specific applications.
Explore our complete range of road marking solutions or contact our technical team for personalized advice. For quick answers to common questions, check out our road marking FAQ page. Any inquiries, feel free to reach out through sales@roadmarkingsupplies.com
Frequently Asked Questions (FAQ)
Q: Is sediment in thermoplastic paint normal?
A: Yes, sediment in thermoplastic paint is completely normal. It is caused by silica sand, a key ingredient that improves abrasion resistance and skid resistance, settling due to its higher density than resins and pigments.
Q: Does sediment affect the quality of road markings?
A: Minor sediment does not affect marking quality if handled properly. Simply stir the paint thoroughly during melting and maintain the correct application temperature (180-220°C) to re-disperse the settled particles.
Q: What is the difference between coarse sand and fine sand in thermoplastic paint?
A: Coarse sand provides better abrasion resistance and faster drying but settles more easily. Fine sand settles more slowly and produces a smoother finish but has lower wear resistance. The choice depends on your specific application needs.
Q: What temperature should thermoplastic paint be heated to?
A: The standard application temperature for thermoplastic road marking paint is 180°C to 220°C (356°F to 428°F). Always follow the manufacturer’s specific recommendations for your product.
Q: How can I prevent sediment from causing problems during application?
A: The two most important steps are: 1) Stir the paint thoroughly after loading it into the melting kettle, scraping the bottom and sides to re-suspend all settled particles; 2) Maintain a consistent application temperature between 180°C and 220°C.
Q: Can I use thermoplastic paint in cold weather?
A: Yes, but you need to use a cold-weather formulated thermoplastic paint that has better low-temperature flexibility. You may also need to adjust the application temperature slightly and ensure the road surface is dry and free of ice.
