Dew point is the temperature at which air becomes saturated and condenses on the surface. Paint should only be applied if surface temperature is at least 3oC above dew point. Relative humidity is also considered to calculate dew point, and a rotative hygrometer can be used for that.
AIR HUMIDITY |
AMBIENT TEMPERATURE ( ºC ) |
||||||||
|---|---|---|---|---|---|---|---|---|---|
0 |
5 |
10 |
15 |
20 |
25 |
30 |
35 |
40 |
|
90 |
-1,3 |
3,5 |
8,2 |
13,3 |
18,3 |
23,2 |
28,0 |
33,0 |
38,2 |
85 |
- 2,0 |
2,6 |
7,3 |
12,5 |
17,4 |
22,1 |
27,0 |
32,0 |
37,1 |
80 |
- 2,8 |
1,9 |
6,5 |
11,6 |
16,5 |
21,0 |
25,9 |
31,0 |
36,2 |
75 |
- 3,6 |
0,9 |
5,6 |
10,4 |
15,4 |
19,9 |
24,7 |
29,6 |
35,0 |
70 |
- 4,5 |
- 0,2 |
4,5 |
9,1 |
14,2 |
18,6 |
23,3 |
28,1 |
33,5 |
65 |
- 5,4 |
- 1,0 |
3,3 |
8,0 |
13,0 |
17,4 |
22,0 |
26,8 |
32,0 |
60 |
- 6,5 |
- 2,1 |
2,3 |
6,7 |
11,9 |
16,2 |
20,6 |
25,3 |
30,5 |
55 |
- 7,4 |
- 3,2 |
1,0 |
5,6 |
10,4 |
14,8 |
19,1 |
23,9 |
28,9 |
50 |
- 8,4 |
- 4,4 |
- 0,3 |
4,1 |
8,6 |
13,3 |
17,5 |
22,2 |
27,1 |
45 |
- 9,6 |
- 5,7 |
- 1,5 |
2,6 |
7,0 |
11,7 |
16,0 |
20,2 |
25,2 |
40 |
- 10,8 |
- 7,3 |
- 3,1 |
0,9 |
5,4 |
9,5 |
14,0 |
18,2 |
23,0 |
35 |
- 12,1 |
- 8,6 |
- 4,7 |
- 0,8 |
3,4 |
7,4 |
12,0 |
16,1 |
20,6 |
30 |
- 14,3 |
- 10,2 |
- 6,9 |
- 2,9 |
1,3 |
5,2 |
9,2 |
13,7 |
18,0 |
Use the following data: supposing room temperature is 25ºC and relative air humidity is 75%, the dew point will then be 19.9 ºC (based on the above table). Thus, no paint should be applied if the surface temperature is not at least 22.9 ºC.