Varying insulation thicknesses

[HalcyonStorm]

Hello.
I am currently investigating the relationship between the thickness of insulation and the temperature of the system being insulated. The material I used was card - not a common insulator, I know, but the variable in question was thickness. What I found was most interesting: for the first 7 minutes or so of testing, using two sheets of card appeared to cause the system to heat slower than just one sheet of card, as expected. After 7 minutes, however, the two seemed to behave exactly the same until around the 20 minute mark. Another curiosity can be seen between the data from 5 sheets of card and 3 sheets - after 30 minutes, the temperatures of their respective systems appeared to be almost exactly the same.

I am currently attempting to theoretically explain my results - does anyone here have any ideas? I have included the graph's spreadsheet as an attachment to the thread.
Thank you!

 

[mfb]

I would expect that your main heating was done somewhere where you did not have the insulation, therefore the number of sheets did not matter much.

In addition, I would not interpret to much in the small differences between your values. While there is some visible trend (lower temperature for more sheets), the time-dependence of the differences is probably just random noise.

 

[256bits]

I have trouble visuallized your setup and have no idea what 'card' is.

But, insulation also has a specific thermal capacity and will abosrb some of the heat and increase in temperature as would any other material.