After purchasing a TC205 sponge and comparing it with the default sponge that came with my soldering station, I noticed that the TC205 sponge is very thin in comparison!
Is the thin sponge used for a different application? What are the slits on the sponges for?
The sponge comes thin as purchased because the cells have been flattened, but once it is wet the cells relax and the sponge will take its final form. There is no difference between thicknesses of sponge as all they are doing is abrading off the solder without damaging the tip. The grooves provide a larger abrasion surface without increasing the volume of the sponge.
Brass wool works a lot better than sponges imo, and doesn't require water.
Try pouring water on it and watch the magic of science LOL.
Seriously it should just expand outwards every which way and look just like (or similar to) the one on the right.
Hey I could be wrong but one I did recently expanded beautifully.
Others have already noted that you just need to add water to expand your new sponge. I wanted to address your second question about the slits. Line them up parallel with the iron when you put the sponge in its tray. Then when you drag the iron tip through the sponge to clean it, it can do a better job cleaning the sides of the tip. Some model sponges have the slits, others don't. I've never found it to make much difference either way.
Brass wool is a correct accessories for cleaning soldering iron. Wet sponges should not be used due to worn out of soldering iron due to temperature difference between iron and wet sponge. Soldering iron will degrade faster while using wet sponges. So it is very clerar whether it is thick or thin, sponges should not be used.
