Clean work
The habits, and the small pile of kit those habits need. None of it is exotic and none of it works on its own: still air, clean hands, short openings, in that order.
Still air box or flow hood
Gives you a pocket of settled air to open sterile containers inside.
Why: Moving air carries spores, and an open jar in a moving room is an open invitation. A still air box does most of what a flow hood does for a fraction of the outlay.
Improvised: A clear storage tub on its side with two arm holes cut in it, wiped down and left to settle for a few minutes, is the improvised version most people start with.
Nitrile gloves
Gives you a surface you are willing to wipe with alcohol between every step.
Why: Skin sheds constantly and you cannot sterilise it. Gloves are less about being clean than about making the wiping habit easy to keep.
Improvised: Hands washed to the elbow and wiped down do the same job if you are disciplined about not touching your face, hair or phone.
70 percent isopropyl alcohol
Wipes down surfaces, lids, gloves and anything that will pass near an opening.
Why: Seventy percent works better than neat alcohol because the water carries it into the cell and slows evaporation, so it stays wet long enough to act.
Improvised: Denatured alcohol at a similar strength behaves the same way. Ninety nine percent does not, so dilute it with clean water before use.
Micropore tape
Seals a plate or a lid while still letting gas through.
Why: A fully sealed vessel either suffocates or sweats. Micropore holds spores and dust out while the culture breathes.
Improvised: Paper surgical tape from a pharmacy is the same material under a different name.
Scalpel or snap-off blade
Cuts wedges of agar and takes clean tissue.
Why: A sharp edge crushes less of what it cuts, and crushed tissue is slow tissue. Blunt blades tear and the transfer sulks for a week.
Improvised: A snap-off craft knife works well because you get a fresh edge by snapping rather than by sharpening.
Lighter or alcohol lamp
Heats a blade or a needle until nothing is living on it.
Why: Flame is the one sterilant that leaves no residue behind. Let the steel cool for a few seconds before it touches anything alive, or you cook the thing you are trying to move.
Improvised: A gas hob and a pair of tongs, if there is no lamp in the house.
Face mask
Keeps your breath out of the work, and keeps airborne mould out of you.
Why: The second half is the important half. The moulds that take a grow are not things to be inhaling in your own home, so a mask goes on before a suspect container is moved, and that container leaves the house sealed.