Graco 309524N Determining Proper Fluid Temperature, To find your fluid’s Under-Boil temperature

Installation

Determining Proper Fluid Temperature

CAUTION

Operating the heater at its highest setting, over 180°F (82°C), for long periods of time decreases the heater life and can cause fluid to dry out; which can clog the heater and result in a poor finish.

Use the lowest temperature setting possible for maxi- mum heater life. Use the chart in FIG. 9 to determine the

Under-Boil®temperature. FIG. 9 also shows the effect of temperature on reducing viscosity. Note that most of the viscosity reduction occurs by 130°F (55°C).

Under-Boil is the Graco method of hot, airless spraying where the fluid is heated to a temperature just under the boiling point of its most volatile solvent.

To find your fluid’s Under-Boil temperature:

1.Pour a small sample into a heat-proof container.

2.Measure and record the fluid temperature and vis- cosity using a No. 2 Zahn cup.

3.Heat water in a large container to 200°F (93°C). Place the sample in the water.

4.At every 10° temperature rise, measure and record the viscosity and temperature. Do this until solvents start boiling off and the viscosity starts to level off, usually 160-170°F (71-77°C).

5.To find the temperature to use in your Under-Boil system:

a.Subtract the lowest viscosity reading from the highest one.

b.Multiply the result by 0.90.

c.Subtract the result from the highest viscosity reading. Find this number on your temperature and viscosity records.

	100
	90
cup	80					Heavy Lacquer
Zahn	70						Medium Lacquer
#2	60
with							Enamel
	50
seconds	40
	30
Viscosity:
	20
	10
	0												oC
	20		30		40	50		60		70		80
	(70)	(80)	(90)	(100)	(110)	(120)	(130)	(140)	(150)	(160)	(170)	(180) (oF)
						Temperature

FIG. 9: Reducing Viscosity: Under-Boil Method

12 309524N