Bed surface

I think I have a pretty easy question. I just built a printer and am wondering if the (I'll describe it as a paper tape like surface of the bed) is okay to print on. It didn't come with glass and am wondering if getting a piece of glass is important? I appreciate the help.

Now that I looked at it closely, I'm guessing it's a metal piece with tape as a cover. I've never not seen a not glass bed. I just want to be sure. The instructions for building the printer were very bad

I have a mk3 heatbed turned upside down with the aluminum side on top. I taped it with 3M blue painter tape and can print pretty well.
I also have glass plates but don´t use them anymore.
For PLA I use 45°C heatbed temperature instead of 70°C for a glass plate.
You can even print PLA on a cold bed, but you might have trouble getting the part off after printing.
-Olaf

Mine is mk2a, going to aluminum bed because I'm going to add inductive sensor for auto bed leveling. You were concerned that the nozzle would crash/scratch the aluminum surface?

The biggest reason for glass is that it provides a reasonably level surface where metal (or anything else) can bend or have high and low spots. This becomes more important the lower the layer height and smaller the nozzle, also the larger the bed size. If it's a small bed (200mm range or less) and you are using a .50mm nozzle then you can easily get away with it if the aluminum is flat.

When you decide you want finer detail and want to move to a smaller nozzle and lower layer heights then it gets more important to have glass.

Also the metal tends to warp a bit when changing temperature, so what is perfectly flat at 25° can be wrecking your calibration at 90°.
But IMHO the best reason to use glass over an aluminium bed is so that it can not be scratched.
Nothing is worse than having cut marks in it because the knife slipped once...

I've had a lot of success with a mk3 aluminium heated bed printing ABS directly on the aluminium surface using extra firm hold hair spray. A good layer of insulation on the underside of the heated bed really helps maintain the correct temperature, im using aluminium foil against the underside of the bed with foil bubble wrap insulation under that, and another layer of foil bubble wrap below the bed to reflect radiated heat back upwards.. I've placed a small square of Kapton tape over the hole in the middle of the bed where the thermistor sits (wishing now I'd bought the version with the surface mount thermistor instead, since this occasionally needs to be replaced and peels away at the corners).

Also if you plan to use an infrared thermometer to double check your bed temperature, stick a square of black PVC insulation tape on one corner, the aluminium's shiny surface gives false readings on the IR thermometer without it.