The data sheet gives a starting point, not a setting. Every job moves it: hose length, outside air, the substrate, the day's humidity. Start here, spray a test patch, and adjust.
Starting settings
| Thermoseal HFO and 5G (closed cell) | Thermoseal 500 (open cell) | |
|---|---|---|
| Primary heater, initial | 110 to 120°F | 129°F |
| Hose, initial | 110 to 120°F | 129°F |
| Processing pressure | 1,200 to 1,450 psi | 1,200 psi |
| Drum temperature | warm gradually to 77°F; do not recirculate | recirculate at 77 to 90°F |
| Mix ratio | 1 to 1 by volume | 1 to 1 by volume |
| Substrate and air | above 45°F summer grade, above 14°F winter grade | above 32°F |
| Substrate moisture | under 18 percent (concrete under 10) | under 18 percent (concrete under 10) |
| Dew point | substrate at least 10°F above | substrate at least 10°F above |
The rig has to be able to hold a consistent 1 to 1 ratio and reach at least 1,200 psi. If it cannot, the problem is the rig, not the settings.
Before the first trigger pull
- Drums at temperature. 77°F is the number. A cold drum is thick, pumps short and throws the ratio off at the first stroke. Closed cell is warmed in the drum, not recirculated; the HFO blowing agent does not like being pumped around.
- Heater and hose at the set point and holding. Watch the hose reading at the gun end, not the display at the machine. A long hose in cold air loses heat; on a cold day run the hose at the top of the range and keep it off the ground.
- Pressures matched. A and B gauges within a close band of each other. A gap that grows while you spray is a restriction on one side: a screen, a chamber port, a check valve or a drum running empty.
- Substrate checked. Temperature with an infrared gun, moisture with a meter on wood, and the dew point from the weather. Frost, dust, oil and rust come off first.
- Test patch. One square foot on a scrap of the same substrate. Watch the rise, the cream time and the surface before committing to a wall.
Reading the foam and adjusting
| What the foam does | Likely cause | Adjust |
|---|---|---|
| Rises slowly, dense, poor yield | Material too cold at the gun, substrate cold | Raise heater and hose within range; warm the substrate; check drum temperature |
| Scorched, dark core, strong smell, surface cracks as it cools | Too hot, or lift too thick, or winter grade in the heat | Lower heat; thinner lifts; switch grade |
| Rough surface, pattern breaks up, "popcorn" | Pressure low for the chamber, or material cold | Raise pressure within range; check heat; check chamber size matches the rig output |
| Spits, pulses, crossover at the gun | Chamber or side seals worn, pressures unbalanced | Service the gun; find the restriction |
| Glassy, brittle, crumbles | ISO-rich: B-side restricted or short | Stop. Check B screen, pump, drum level |
| Soft, spongy, slow to cure, fishy smell | Resin-rich: A-side restricted or short | Stop. Check A screen, pump, drum level |
Change one thing at a time. Ten degrees of heat or 100 psi is a step; then spray another patch.
Cold-weather setup
- Winter grade on the closed cell, and still warm drums; the grade handles the wall, not the drum.
- Run heater and hose at the top of the range and insulate the hose where it crosses open ground.
- Heat the space ahead of the crew where it is possible; the substrate warms slower than the air.
- Spray the sun side of the building in the afternoon and the shaded side after it has had the morning to come up.
The data sheets say it plainly: the applicator manufactures the foam on site and is responsible for observing it and adjusting. The settings above are where that starts.
Quick answers
What temperature do you spray Thermoseal HFO at?
Start the primary heater and hose at 110 to 120°F with 1,200 to 1,450 psi, drums warmed gradually to 77°F and not recirculated. Adjust from there by what the foam does at the wall.
What pressure do you spray open-cell spray foam at?
Thermoseal 500 is sprayed at about 1,200 psi with the heater and hose at 129°F and the drums recirculated at 77 to 90°F. The rig must hold a 1 to 1 ratio by volume.
How dry does the wall have to be before spraying foam?
Wood and most substrates under 18 percent moisture, concrete under 10 percent, and every substrate at least 10°F above the dew point and free of frost, dust, oil and rust.