best option for smooth glass first layer  

The smooth PEI sheet.

I take it you have received the textured sheet (Which personally I would only use for PETG and TPU).

PRUSA do a smooth spring steel PEI sheet or look on Amazon and type Prusa Mk3 then search for a spring steel sheet with PEI adhesive sheet

eg https://www.amazon.fr/Gaoominy-LImprimante-Plate-Forme-Imprimant-Construction/dp/B089GKRCFM/ref=sr_1_51?__mk_fr_FR=%C3%85M%C3%85%C5%BD%C3%95%C3%91&dchild=1&keywords=prusa+mk3&qid=1591174381&sr=8-51

But I cannot comment on the quality of these, sometimes you may get a good one sometimes not.

hi,

thanks for your feedback. 

i have the prusa PEI sheet witch is really good but produce a mat finishing, but i prefer a glossy finishing like with a glass. because my first layers are put on front of walls 🙂

i am selling 3D printed art that are hanged on walls 🙂

i really love my prusa printer. thanks to the prusa tea for their work !

Would it not be just as easy to spray the finished face with gloss lacquer as not all filament is capable of a glossy finish especially PLA.

For glossy finishes you really want to be using PETG and at the higher end of it's temperature, which can cause stringing, also with no cooling.

Posted by: @impression3d

[...] what is the bed option to have a smooth and glass effect first layer? without using a glass 🙂

I have seen some very nice prints (on other printers) with mirror-smooth first layers printed on glass. The surface is almost mirror like. They are absolutely beautiful, but that result is not easy:

• You need a perfect flat piece of glass. This is not as easy as it sounds and you won't know the glass is smooth enough until you try it.
• No prep can be used on the glass. The finest coating will distort the finish.
• Your first layer calibration has to be perfect. Too high and there will be small gaps between extrusions. Too low and they'll be squished and distorted.
• You have to get it off the glass without damaging the finish.

So while I won't say what you're trying to do is impossible, I can say it's not easy. You can get close on a Prusa with the smooth PEI surface, but it will work best with a new PEI sheet (no sanding, very little prep) and it won't be as shiny. As @chocki suggests, some post-processing is probably much easier and less error-prone. Alternately, check out what people have done with textured print surfaces.