Re: Thermal Images of Various Bed Setups
It is about 20 min for it to heat up with glass. Would putting some aluminum foil between the aluminum and ceramic help with heat transfer, or no? Also, do I still need hairspray? Is it really worth the switch from glass to ceramic?
I use a dusting of hairspray.
The main advantage of ceramic over 'ordinary' glass is - glass has almost no thermal mass and is not uniform in its distribution as a result (it will have high intensity spots with sharp drop off across the plate) and its thermal conduction is measured in the 0.8-1.0 realms .... Borosilicate glass has a slightly higher transmission value (making it a better conductor than 'ordinary' glass), due to its annealed surface (1.05->1.2). This also improves its heat uniformity, but its still a 'lightweight' in thermal mass stakes. What this means is a change in the heatbed is rapidly reflected to the glass and its upper surface - turn the heatbed off and the glass will cool in a matter of minutes..
Ceramic Tiles on the other hand, depending on the specific composition, can have 4,5,10,20 times the heat conduction capabilities of glass, whilst also having much larger thermal mass - it takes longer to observe a change as a result of changes to the heat intensity, but as a result, it is far more uniform and gradual in its temperature changes... switching off the heat bed and leaving the tile for 10 minutes can see it still with a temp of 60°C....
Granite Tile is anywhere from 1.7->4 as a thermal conductor... so again, 1.5 to 4 times 'better' than glass.... only problem with granite is they tend to be large tiles...
So whilst it takes a tad longer to heat up than glass - it does so with far more uniformity and will also not fluctuate during a print as much as glass does (for example, when the bed is at the bottom of its PID cycle, glass will observe say a degree change in temp, where as tile will stay at the setpoint whilst PID bounces around... I found this has a HUGE impact on curling/warping/lifting... I just dont get that happening on ceramic tile, where as I do on Glass/Aluminium (Alu being the opposite end of the scale and *too* good of a conductor..... it retains no thermal mass and needs constant application of a heat source to maintain temperature - but heck it'll get there fast 
)
All I can say is, play with it for a bit, experiment over a few days, and I'm pretty sure you'll be impressed with a tile over glass....
