Testing the surface temperature of paint colours to give an indication of the effect it has on your native bee hive when exposed to full sun.
Dark paint can get quite hot, but how much heat actually transfers through the timber?
The insulation properties and thickness of materials can greatly reduce the transfer of heat to the colony inside the box, eg. Styrofoam provides great insulation and hardwood has poor insulation properties because it’s dense. In this test we’re using Hoop Pine which is a lighter wood with good insulation properties.
- This is not a technically scientific way to test temperatures but will still give a good indication of how colours affect the temperature of a native bee hive.
- This is not a hot time of year. Another test will be done in Summer and we may see bigger differences.
- Inconsistent timber density will affect the transfer of heat to the back and will result in slightly different temperatures.
- It’s likely the back temperature could be all similar to each other due to the Ambient temperature and the only differences we might see is if the front temperature is so high it raises the back temperature more than the rest.
- This is a simple test to give indications using single pieces of timber. Full hive boxes will give different results.
- Allow for variables. Don’t focus on exact numbers but more the general trend.
The Sample Rack: When the samples are sitting on the tip of the pins there’s minimal contact points and they are fairly well isolated from each other and the rack holding them so there should be minimal transfer of heat.
Photo: in order from coolest to warmest
20 April 2025 / 12pm / Ambient 28.9°C. Table shows colours in order of surface temperature, exposed to full sun. After a few hours exposed to full sun a infrared thermo gun was used to check the surface temperatures on the front and back.
| Paint Colour | Front Surface Temp °C | Timber Thickness | Back side Surface Temp °C |
|---|---|---|---|
| 1. White | 32.5 | 33mm | 30.2 |
| 2. Pale Yellow | 34.5 | 33mm | 30.4 |
| 3. No Coating – Uncoated Hoop | 35.9 | 33mm | 30.1 |
| 4. Light Tan | 40.5 | 33mm | 30.8 |
| 5. Bright Yellow | 40.3 | 33mm | 30.4 |
| 6. Heavy Duty Clear Coat | 41.9 | 33mm | 31.2 |
| 7. Bright Blue | 44.1 | 33mm | 31.5 |
| 8. Dark Green | 47.8 | 33mm | 31.9 |
| 9 Black | 53.1 | 33mm | 32.5 |
| 10. Red (future sample) | – | – | – |
20 April 2025 / 12.30pm / Ambient 28.9°C. Comparison Table for different thicknesses. *During the middle of Summer at 38°C Ambient timber thickness may make more difference here.
| Paint Colour | Front Surface Temp °C | Back Temp°C / 25mm | / 33mm | / 38mm |
|---|---|---|---|---|
| White | 33.7 | 31.5 | 30.5 | 29.9 |
| Black | 54.2 | 33.5 | 33.1 | 32.4 |
It’s interesting that even though the outside painted surface can be hot there’s minimal transfer of heat through the timber. We would generally say that the thicker timber will provide better insulation. It seems obvious doesn’t it, but if it’s obvious we should be able to demonstrate it somehow. I think the last line in the table showing the black sample with 25/33/38mm timber does show that, and hopefully we see more significant differences in the peak of Summer.
It would be good to do a test with a full hive box painted black, but I don’t want to paint one black!
It’s not the end of the world! If you’re native bee box is painted a dark colour, keep it out of full sun in Summer or make sure it has a big shady roof. There’s plenty of dark coloured boxes out there that work perfectly well.
