For the inexperienced there are some warning signs that the man’s penis is about to ejaculate. There is a good description made by Jeff (his nice blog is unfortunately inactive):
“The testicles will tighten significantly just before ejaculation (about 5-10 seconds). The shaft of the penis will suddenly become stiff and rigid, more so than throughout your ministrations (about the last 2-3 seconds). The head of the penis will suddenly engorge with blood, swell largely and the penis shaft will feel like its gone rigid and is straining against itself (which it is) (approximately 1-2 seconds).
The last and final clue is that you will feel the cum-tube or center ridge on the underside of his penis shaft suddenly pulse. It will give one (empty of sperm) pulse, followed a fraction of a second later by a second and then subsequent pulses. The first pulse generally does not ejaculate semen; the second and subsequent pulses most assuredly do ejaculate semen and a majority of the semen is ejaculated during the first three contractions (1/2 -1 seconds). The remaining contractions and pulses of semen will diminish in volume.
- First contraction/pulse: usually devoid of sperm (empty pulse);
- Second contraction/pulse: contains sperm (approximately 1/8th of the total volume);
- Third and fourth contractions/pulses: contain sperm (approximately 1/3 of the total volume), this is the heaviest flow of semen during the ejaculation;
- Fifth, sixth, seventh and eighth contractions/pulses: contain sperm (approximately 1/2 of the total volume);
- Ninth and subsequent contractions/pulses: may or may not contain sperm and are sometimes referred to as 'after waves' or the penis attempting to continue to ejaculate sperm when little or none remains.”