What causes hot melt stringing?
Stringing (also called angel hair or cobwebbing) happens when the bead does not cut off cleanly at the nozzle. Typical causes are glue running too cool, a nozzle too far from the board, a worn or partly plugged nozzle, low air to the gun, cold board, or drafts. Check them in that order. If it keeps coming back, the grade may not suit your line; call 800-249-0337.
Stringing usually has more than one cause. Typically, it means the line has drifted out of the glue’s operating window. Work through the checks below one at a time so you know which change fixed it.
Hot melt and hot equipment can cause burns. Follow your equipment maker’s safety manual and lockout steps; qualified personnel only. Call us for data sheets
Checks, in order
| Likely cause | What to try |
|---|---|
| Glue too cool (viscosity too high) | Verify actual temperature at the tank, hose and gun, not just the setpoint. Raise in small steps, staying inside the grade’s recommended range. |
| Nozzle too far from the board | Keep the nozzle close to the board, as your equipment maker says. The farther the glue travels, the more it strings. |
| Worn, charred or partly plugged nozzle | Clean or replace the nozzle and check the shutoff. Char is a common cause; see charring and gelling. |
| Low air to the solenoid or slow gun | Check incoming air pressure, mufflers and solenoid condition. Keep solenoid air lines short. |
| Cold board or drafts | Let stock reach room temperature before running. Shield guns from fans, open doors and HVAC. |
| Bead too long | Trim the pattern so the glue stays under the flap. |
When it is the glue
If temperature, distance, nozzle and air are all in spec and it still strings, the grade may be too viscous or too elastic for your guns. Cattie can match viscosity and set speed to your applicator. Our low-temperature grades typically apply at about 250°F, not 350°F; see low-temp vs standard hot melt before you switch, since the window is different.
What to send us
The grade you run now, tank/hose/gun setpoints, applicator type (wheel, extrusion or jet), nozzle size, line speed, and a photo of the stringing.
Request a sample Call 800-249-0337 Request a quote
Related
How to solve hot melt application problems · Hot melt application trouble-shooting tips · Hot melt system trouble-shooting tips · Hot melt adhesive · Pop-opens · Charring and gelling · Bubbles in the bead
Hot melt stringing FAQ
What is angel hair in hot melt?
Angel hair is fine strands of hot melt that form when the bead does not cut off cleanly at the nozzle. It is the same problem as stringing, and builds up on guns, guides and cases.
Should I just turn up the temperature?
Only in small steps and only within the grade’s recommended range. Running too hot speeds up char and gel in the tank, which can make stringing worse over time. Check nozzle distance, nozzle condition and air first.
Can cold board cause stringing?
Yes. Cold board cools the glue too fast at the nozzle and the bead does not break cleanly. Let stock reach room temperature and keep drafts off the guns.
Will a different hot melt fix stringing?
Sometimes. If the line is in spec and it still strings, a grade with a different viscosity or set may cut off cleaner. Call 800-249-0337 for a grade match and sample.
