Editing Petri dish (section)

== Features and variants ==
{{Cite check section|date=March 2020|reason=every citation is a page to purchase one of the dishes. Needs publications stating the relevant statements instead.}}

Petri dishes are usually [[cylinder (geometry)|cylindrical]], mostly with diameters ranging from {{convert|30|to|200|mm}},<ref name=fisch4909050/><ref>(2019): "[https://www.auxilab.es/en/laboratory-equipment/petri-dish-200-mm-borosilicate/ Product BRB011: Petri Dish 200 mm, borosilicate]". Rogo-Sampaic online catalog. Accessed on 2019-10-25.</ref> and a height to diameter ratio ranging from 1:10 to 1:4.<ref>(2019): "[https://www.fishersci.com/shop/products/corning-gosselin-100-x-25mm-bio-agricultural-petri-dishes-2/p-4494233 Product BTX9302 Corning 100 x 25mm bio-agricultural Petri dishes]". Fischer Scientific online catalog. Accessed on 2019-10-25.</ref> Four sided versions are also available.<ref name=thomas1219C98>(2019): "[https://www.thomassci.com/E-K/Cell-Culture/Dishes/_/Square-Petri-Dish-w/-Grid1?q=Vented%20Petri%20Dish Item 1219C98: Square Petri dish w/ grid]". Thomas Scientific online catalog. Accessed on 2019-10-25.</ref><ref name=fisch11708573>(2019): "[https://www.fishersci.co.uk/shop/products/gosselin-square-petri-dish/11708573 Product 11708573: Gosselin Square Petri Dish]". Fischer Scientific online catalog. Accessed on 2019-10-25.</ref>

Petri dishes were traditionally reusable and made of [[glass]]; often of heat-resistant [[borosilicate glass]] for proper [[Sterilization (microbiology)|sterilization]] at 120–160 [[celsius|°C]].<ref name=fisch4909050>(2019): "[https://www.fishersci.com/shop/products/pyrex-reusable-petri-dishes-complete-6/p-4909050 Product 4909050: PYREX reusable Petri dishes: complete]". Fischer Scientific online catalog. Accessed on 2019-10-25.</ref>

Since the 1960s, [[plastic]] dishes, usually disposable, are also common.<ref name=fischBP94S01>(2019): "[https://www.fishersci.com/shop/products/corning-gosselin-100-x-15mm-polystyrene-petri-dishes/p-5162666 Product BP94S01: Corning 100 x 15mm Polystyrene Petri Dishes]". Fischer Scientific online catalog. Accessed on 2019-10-25.</ref>

The dishes are often covered with a shallow transparent lid, resembling a slightly wider version of the dish itself.  The lids of glass dishes are usually loose-fitting.<ref name=fisch4909050/>  Plastic dishes may have close-fitting covers that delay the drying of the contents.<ref name=fisch09-720-500>(2019): "[https://www.fishersci.com/shop/products/fisherbrand-disposable-petri-dishes-pad-dishes-8/p-3219248 Item 09-720-500: Fisherbrand disposable Petri dishes]". Fischer Scientific online catalog. Accessed on 2019-10-25.</ref>   Alternatively, some glass or plastic versions may have small holes around the rim, or ribs on the underside of the cover, to allow for air flow over the culture and prevent [[Water vapor#Condensation|water condensation]].<ref name=fischSB93102>(2019): "[https://www.fishersci.com/shop/products/gosselin-100x15mm-petri-dish-three-vents-optimized-automation-2/p-8015709 Item SB93102: Corning 100x15mm Petri dish with three vents]". Fischer Scientific online catalog. Accessed on 2019-10-25.</ref>

Some Petri dishes, especially plastic ones, usually feature rings and/or slots on their lids and bases so that they are less prone to sliding off one another when stacked or sticking to a smooth surface by suction.<ref name=fisch09-720-500/>

Small dishes may have a protruding base that can be secured on a [[microscope]] stage for direct examination.<ref name=fischPD1504700>(2019): "[https://www.fishersci.com/shop/products/emd-millipore-petrislide-containers/PD1504700 Product PD1504700 MilliporeSigma PetriSlide for contamination analysis]". Fischer Scientific online catalog. Accessed on 2019-10-25.</ref>

Some versions may have grids printed on the bottom to help in measuring the density of cultures.<ref name=hecht41044  >(2019): "[https://www.assistent.eu/en/product/petri-dishes-made-of-glass-with-grid-and-cover/ Item 41044: Petri dishes made of glass with grid and cover]". Assistent (Karl Hecht) online catalog. Accessed on 2019-10-25</ref><ref name=thomas1219C98/><ref name=fisch11708573/>

A [[microplate]] is a single container with an array of flat-bottomed cavities, each being essentially a small Petri dish.  It makes it possible to inoculate and grow dozens or hundreds of independent cultures of dozens of samples at the same time.  Besides being much cheaper and convenient than separate dishes, the microplate is also more amenable to automated handling and inspection.

Some plates are separated into different mediums known as biplates, triplates, and quadplates.