Caulking is a wonderful way to save you money. When the caulking that you have on your tub starts to wear off, water can enter behind your tub and cause problems like mildew. Also water creeping behind your tub can cause other problems which will lead you to a call to your local repairman. If you properly caulk your tube before this happens you can save yourself a lot of time and money. When you see cracks in the caulk or loose caulk you should get ready to repair it. Caulks are combination of a glue and a sealant. The caulk will adhere to the surface you put them on and they will prevent water from getting behind it.
Type of Caulk
When shopping for a type of caulk you need to make sure that it is meant for indoor/bathroom use. Sometimes outdoor caulks work, but remember outdoor that the caulk is made for a different environment and will act differently. It will better just to stick to an indoor caulk. Also try to find one that has Microban. Microban helps prevent the growth of Mildew; this means you have to re-caulk less often.
There are two main types of caulk: Latex and Silicone. One advantage to using latex caulk is that it is paintable because it dries hard; sometime the color caulk dries off will clash with the bathroom color scheme. Once the caulk is dry you can just paint over it. Another advantage to Latex caulks is that if you make an error it is easier to fix. You can wipe of the latex caulk easily and reapply it.
Silicone caulk is not water based so it is more water resistant. When the caulk dries it dries soft. The next time you try to install caulk silicone caulk will be easier to remove. The downside to silicone is that it will not come of your fingers. The only way to get it off is to wait for your body to naturally remove it. That being said, if you can keep it off of you, then silicon caulk is better for this job.
There are two ways to re-caulk; place new caulk over the old one or remove old caulk and then place the new caulk. Replace the caulk it will last longer; but if all you need is a touch up you can just place the new caulk over the old one. I am not going to focus on touching up the caulk, but all you need to do for that is make sure the old caulk is very dry. Then just place the new caulk over it.
To replace the caulk, first you need to use a good shower cleaner to remove any soap scum around the caulk. Make sure the area is dry before continuing. This will ensure that the tiles are less moist.
Removing Old Caulk
Try and find out what kind of caulk was used before. If the caulk is rubbery then it was Silicon; if the caulk is hard then it is Latex.
Removing silicone based caulks is easier. All you need is a sharp utility knife. Start cutting the old caulk but make sure that you do not go too deep or you will damage your wall.
Too remove latex based caulks you may need to use a heat gun at about 300oF or slightly lower.
Keep moving the gun in order to prevent damage to the tiles. Once all of the old caulk is soft, use the same cutting method as used for silicone.
Once the old caulk is all gone use denatured alcohol to clean the area again; leave the alcohol on the wall for a few minutes. This will remove anything that was missed during the first cleaning you did. If there is still mildew on the wall, you might want to use a mildew killer. The combination of alcohol and mildew killer should give you a clean wall. Also if everything is gone, you will have to re-caulk less often.
Applying the New Caulk
You can either wait for the wall to completely dry and re-caulk the new day or if everything is dry now, you can go for it. If you old caulk was cracking or falling off it might be best to wait till everything is completely dry (use your best judgment). Also if you are using silicon you might want to wait till the next day. If you are only re-caulking because of mildew and not due to crack formation, and using latex caulk, you can start now. Remember to use you best judgment, it will vary from situation to situation.
Make sure you can do the whole job in one sitting, otherwise the caulk may dry with small cracks that mildew can enter threw. When starting the job, spread the caulk evenly throughout the entire region. You can buy a little tool to spread the caulk or just use your fingers. If you use your fingers, keep them moist so no caulk sticks to them. Honestly, that is all you need to know. It will take time to spread all the caulk, but once it is done it is done. Check the whole surface and make sure there are absolutely no cracks. If you find a bad section you can remove latex caulk easily with a finger and attempt to reapply. If you are using silicon caulk try using a towel to remove it. Then reapply.
If you are using latex caulk keep a wet sponge by you so you can remove any caulk that is accumulated on your hands.
If you are using silicon caulk use a towel to wipe of any caulk on your hands. Remember that this kind is not water-washable.
Now just wait at least ten hours, preferable more, for the new caulk to dry. That is it, you are done and just saved yourself a lot of money.