It had to be a glycerin /soapy enema, but not just a "standard" mixture, when I was experimenting with different strength and volume combinations. I had determined that the volume had to be less than 4.0 liters for either glycerin or soap (Ivory) individually (to provide enough room for the contractions to squeeze the incompressible solution through the colon). I had also determined that my toleration limit for glycerin enemas was about 30% strength (even when well mixed the nausea could be very strong). There is also a strength limit for the soap but it's nearly at the point where the soap congeals within the tube as it cools flowing down the tube from the bag (which is about 50 grams per liter). But the combination of both is particularly potent when mixed.
The maximum limit I kinda found for myself was 40 grams of Ivory soap per liter in a 25% strength glycerin solution. Very potent and I had to plan for several hours to get through the clean out, the rinse, and the general abdominal distress after the enemas. So, knowing that, I generally went with a weaker combined solution of 10-15% glycerin and 30 grams per liter or less of Ivory soap.
One night I decided that, rather than mixing the solution into a homogeneous mixture, I would "layer" the glycerin in the bottom of a clear bag being certain to fill the tube and the Higginson pump to the nozzle. Then I mixed the soapy mixture and carefully poured it on top of the glycerin on the bottom of the bag. Of course the glycerin was room temperature and would flow relatively slow out of the bag (hence the need for the pump). With a double balloon nozzle inserted and inflated, I opened the clamp and began the flow. I think it was a 3.5 liter enema of 20% nominal strength (700 ml). But I was using my rectum as the mixing chamber and most of the glycerin entered me before the soapy solution "broke through" the glycerin layer.
When the soapy solution broke through, I could feel the warmth of the solution passing into my colon as it carried a variable strength solution up into my colon. I did drain the bag but the reaction was pretty interesting. My rectum felt "tingly" and eventually the cramps became very strong. Waves of nausea began to occur and eventually I had to release the enema with a trash can in front of me. The glycerin apparently closed my rectum down to a small diameter because even with the nozzle removed, expelling the enema was very difficult. Fortunately, the soap had done a good job of dissolving whatever was in my colon. I was sweating profusely and my watch gave me an abnormal heart rate warning. Eventually, I expelled enough to lose the feeling of fullness but I wanted to stop the nausea and cramps but rinsing or diluting the solution within.
It was almost impossible to insert a narrow nozzle to rinse or a provide dilution of the solution. Eventually, I did thread one in and begin a warm water rinse. It took several warm water rinses to reduce the coating of glycerin in my rectum and lower colon. The cramps did not subside but the nausea did. After an hour of fairly intense cramps, I was finally able to provide my first higher volume rinse using baking soda. It took me a couple of hours to finally rinse out enough and calm my colon. I was very cleaned out after about four hours.
Although I still give myself soapy glycerin enemas (mixed), I haven't done this method since this experience.