Slime is two stains, not one.
Household slime is polyvinyl acetate - ordinary white school glue - loosely cross-linked by a borate. The cross-linking is what turns a runny liquid into a mass that stretches, holds its shape, and clings. It is also, usefully, mechanical rather than chemical: the network holds the glue together, but it never bonds to the wool. The mass sitting on your rug is a guest, not a resident.
The color is the resident. Every slime carries a colorant, and the ones in kits and kitchen recipes are usually food dyes - the same acid-dye family a mill would reach for if it wanted to color a wool carpet. Glitter and foam beads ride along as inert passengers. So the problem in front of you is really two: a polymer mass that will come off if you are patient, and a dye that is looking for somewhere to bind. Which of those two you are treating at any given moment decides whether an instruction helps or harms. Our guide to which rug stains survive and which do not sets out that triage across every category; this page is the slime chapter of it.
Why the carpet answer is a dye bath.
Wall-to-wall carpet in a family house is usually solution-dyed polypropylene or nylon. The color lives inside the filament, the surface is close to non-absorbent, and a dye that lands on it has nothing to hold on to. Flush it with hot water, agitate it with a brush, and it leaves. Every step of that advice is sound on that material, and the people writing it are not being careless.
Wool is the opposite material. It is a protein fiber, and its structure carries sites that bind acid dyes - which is precisely why wool has been dyed for several thousand years and why the color in a good rug stays put. Those sites open under two conditions: heat and acid. Warm vinegar supplies both at once. That is not an analogy; it is the method. A dyer heats a wool bath, drops the pH with acetic acid, introduces an acid dye, and the fiber takes the color permanently. Pouring hot vinegar onto slime on a wool rug performs that same process at small scale, with your rug as the goods and the slime as the dyestuff.
The same inversion governs the other household accidents whose standard remedy is a bottle - paint, ink, and nail polish, which we take together in the solvent-stain guide. Here the heat is the half people underestimate, and it is the same reason steam cleaning is the wrong tool on a hand-knotted rug. Solvents are the other half. Alcohol and acetone do soften the glue, but they also mobilize dye - the rug’s own as readily as the slime’s - and a mobilized dye travels outward along the wet edge. That is how a coin-sized green spot becomes a hand-sized pale patch with a colored rim, which is a color-bleed problem rather than a slime problem, and a considerably worse one.
The first ten minutes.
Begin by lifting, not pressing. Slime cross-links to itself far more strongly than it grips wool, so a fresh mass will often peel away from the pile in one piece if you take hold of the edge and pull it slowly back over itself. Pressing does the opposite: it forces the polymer down between the yarns and onto the foundation, where the only route out is upward through the pile.
Whatever remains, chill. Seal ice in a bag and rest it on the spot for a few minutes until the slime stops being stretchy and turns crisp. Cold is doing real work here - the same work it does on candle wax - by taking the material below the point where it can flow, so it fractures instead of smearing. Use the bag rather than ice directly; melt water is the one thing you do not want soaking into the spot.
Then fracture and lift. A spoon handle, a butter knife held flat, a plastic scraper - anything with a blunt edge and no teeth. Work from the outside of the mark toward its center so you are shrinking the stain rather than widening it, crack the brittle slime, and lift the pieces off. Vacuum between passes with strong suction and no beater bar, and re-chill whenever the remainder turns tacky again. Two or three cycles usually take out everything that is going to come out mechanically.
The film underneath.
What is usually left is a thin, slightly stiff film of glue on the fiber, detectable more by touch than by eye. Polyvinyl acetate softens in water, so this part does want moisture - but cool water, and as little of it as the job needs. Damp a white cloth, add a drop of a pH-neutral detergent labeled safe for wool, and press it into the spot; wait; then blot with a dry cloth. Repeat with clean sections until nothing more transfers. Blotting, never rubbing: rubbing splays the yarn tips and leaves a fuzzed patch that catches the light differently ever afterward, long after the stain itself is forgotten.
Keep the wet area small and dry it promptly with a fan. A hand-knotted rug sits on a cotton foundation, and a cotton foundation that stays damp browns from within and can wick the surrounding color into the wet edge as it dries. Over-wetting a spot is one of the commonest ways a household repair turns into a bench repair - the same mechanism described in our guide to cleaning a rug in place. If you find yourself adding more water because the last round did not finish it, that is the signal to stop rather than the signal to continue.
What to do about the color.
Here is the honest part. Once the mass and the film are gone, any color remaining is dye that has bound to protein fiber, and no amount of further cleaning will lift it - cleaning removes what sits on a fiber, and this is now part of it. The tool for a bound dye is controlled reduction: a chemistry that breaks the dye molecule itself, applied at a measured strength, at a measured temperature, on a rug that has been dye-tested first so the reduction takes the slime’s color and leaves the rug’s. That is bench work, and it is the same discipline behind color restoration.
The odds are decided mostly by what happened in the first hour. A pale food coloring, caught the same day, never heated, usually reduces until you cannot find where it was. A saturated slime left through a weekend, or one that has already met hot water, often leaves a shadow: lighter than it was, visible if you know where to look, and permanent. We will tell you which of those two you have after inspecting the rug, and we will tell you before any work begins rather than after.
Where to stop.
Three signals. The first is a colored edge creeping outward from the spot - that is dye on the move, and every further minute of work enlarges it. The second is the pile going fuzzy or matted where you have been working, which means the wool itself is being damaged and the stain has stopped being the main problem. The third is simply the rug: if it is hand-knotted, antique, silk, or a piece you would be sorry to lose, the correct first response is to lift what lifts cold and then leave it alone.
At the bench the same rug goes into a full hand wash with temperature and pH set for its fiber and its dyes, dye-tested before water touches it, and dried flat - which is also, incidentally, the only way a spot is treated without leaving a clean ring around it. Between accidents, the routine care in our wool rug guide is what keeps a rug in the condition where one bad afternoon does not matter much. Every piece is inspected by hand before any work begins, and if the honest answer is that the mark will not fully go, you will hear that first.