I just thought I'd share what we are doing for our sway---a modified swim down technique. We've been TTC blue since November of 2010. In that entire time, we were never able to get the egg white to float, no matter what we did. We tried every method on here multiple times, but it didn't work for us. So, we decided to go with our 'floaty semen' and try a swim down method.
We collect dh's sample in an unlubricated/non spermicide condom, then dump it in a small container. We get an eggwhite with the correct ph (9.0-9.9) then separate out the thicker part of the egg white. Some eggs have a runnier part and a jelly-like part to the white. We've found that our sperm swim better in the thin part. We use a tiny syringe to fill the bottom of the test tube with the thin egg white. Then, we use the syringe to layer an equal amount of semen on top of the egg white. So-----egg white is in the bottom towards the floor, semen in the top towards the ceiling. The sperm want to go somewhere, so they enter the egg white swimming DOWN towards the floor.
We use 3 test tubes to do this, hopefully increasing the surface area and amount of sperm per each tube of egg/semen. We think we get more sperm this way instead of with one test tube. We do NOT put the test tube in at an angle. We keep ours straight up and down. We decided we feel more confident about being able to separate the layers after the incubation period when they are straight up and down. When the test tube is angled, we think we see too much mixing of the egg white and semen when we lift it out of the incubator. It's really hard to not move it even a fraction if you're trying to keep it at that same angle. This might not work for everyone, but we think the up and down orientation, rather than slanted, makes a better sort for us.
We mark the test tube with a thin sharpie marker to show where the semen meets the egg white. Then, we draw lines that divide the egg white into 5 sections-----20% each.
After 1 hours in incubation at 97-98.6 degrees (a slightly lower temp has shown us more active swimmers, but I'm sure everyone's sperm is slightly different), we take out the test tubes. In our more successful sort, we can slightly see the sperm moving down into the egg white layer. It almost looks like rain falling from rainclouds at a distance. We siphon off all the semen with a syringe and discard it.
Now we're left with just egg white (and hopefully a bunch of fast xy sperm). We look at it this way----the farther the sperm can move into the egg white, the faster they must have swum. The shooting star sperm (super fast xx) will be at the very bottom of the egg white, closest to the floor. The middle layer should hopefully contain mostly xy sperm. The very top layer of egg white (closest to the ceiling and closest to the semen before we siphoned it off) should contain mostly xy sperm, but maybe several xx sperm, also.
We suck up the top 20%, then the middle 3- 20%, 20%, 20%, then bottom 20%. We use 5 separate syringes to suck up the egg white. We put a tiny drop of each of these samples on a pre-labeled slide and look at them under the microscope. Usually, the very bottom layer has a few really fast, straight moving sperm. Since we can't be sure whether or not these are xy or xx, we discard this layer. The next 3 layers in the middle typically have straight, fast moving sperm. The top layer, the one that was closest to the semen, usually has a mix of xy and xx. We typically discard this layer.
So, during most of our attempts, we use the middle 3 layers, the middle 60%, discarding the 20% at the bottom and the 20% at the top. We'll have more sperm if we had a 4 day cut off, and fewer if we collected his sample from 24-48 hours.
I hope this wasn't too much info, but I wanted to be detailed since the process can be pretty confusing.