There are 2 steps which you want to take to clean a large needle point rug. Also keep in mind that you may have some foot traffic patterns with which to be concerned.
First off, you want to get some plastic sheeting to put beneath the rug if it isn’t on a water-proof floor, for example vinyl. You will need some frothing carpet cleaner and a rug cleaning machine that does not have revolving bristles. If the machine contains an upholstery tool, you can use that as long as it does not have any revolving bristles. When it comes to cleaning a needlepoint rug, consider it as a large piece of upholstery that needs to be cleaned.
Before you use the foaming carpet cleaner, do a spot test in a small subtle location to make sure of its color fastness. Spray on the froth, then let it sit for 10 or 15 mins, then wipe it up with a humid rag. Do not scrub the area ; wipe it up carefully. Do not continue if there’s any color in the foam, other than the dirt from the surface. If the spot test turns out fine then you can use the foam on the other areas. Although the directions on the can may instruct to clean the foam into the rug, do not do so with a yarn rug. Instead use a damp material and work it around a little so that it will supply the surface with satisfactory coverage. Then let it sit for 10 mins or so, then wipe the surface with a humid rag to remove the foam. Then wipe the surface carefully with a slightly wetter rag, and wash it frequently.
After that spray adequate froth over the whole rug so that it will spread from one end to the other. Don’t spray a thick layer of foam, but merely enough to cover it. Then work it around thoroughly with a moist fabric ( as before ), then let it sit for roughly 10 mins. At that point, the foam should be just about gone. Then go over the surface with the carpet machine and halfhearted water. Suck out as much water as possible as the rug shouldn’t be sopping wet. Also, don’t rub hard on the surface of the rug when it is damaged as the yarns could get damaged.
The rug should dry as fast as possible . For the original drying, you may hang it up outside over a line or railing. If you are not able to do so, put towels under the rug and set up a fan to blow across the top. When the rug is terribly close to becoming dry, take it off the line and lay it on the floor where it can dry flat. Do not walk on it or place furniture on it till the rug is completely dry. More carpet cleaning tips here.