Some of our viewers have some patching to do on their bathtubs. Here are the tricks, but remember that a patch almost always shows and some do not last forever so if you really want it nice without replacing the tub you will want to hire a professional refinisher who has special equipment and special paints.
Whether it is fiberglass or porcelain over steel you should use a grinding stone in a rotary tool, or some emery cloth and a lot of elbow grease, to clean out the chip and even grind off a little of the area around the chip. For a fiberglass tub you need a fiberglass patch. That means a fiberglass cloth and an epoxy resin. If you cannot find such a kit at the hardware store, go to the car store -- that is one of the ways we fix car bodies. Don't try to fill in a gouge with the resin, but rather put on a second glass cloth patch, smaller than the first one if you still have a dip.
For a steel tub, grind down to bare metal before putting on the porcelain touch-up liquid. Put on very thin coats, let it dry, sand a bit and do it again until it is a level surface. To get the right colour with the touch-up products you can mix two tubes of different colours together.
One viewer wanted to know how to remove a tub without damaging it. That is a very good question because the tubs are usually nailed to the studs and if you use a crowbar to remove them you are guaranteed to chip something. Either punch the nails right through the tub rim into the stud, or use a drill to drill the head off of the nail. Then you can simply lift the tub out.
Take a look at the technician from Bathmaster in North York, Ontario as he is refinishing a tub back at the shop. What I want you to realize is that he grinds or blasts the old finish right off, then applies industrial strength liquid enamel to the tub, requiring special ventilation and a full suit of protective gear. If they do this in your house, they will close off, ventilate and wear the same protective gear. That just helps to show you that you will not get the same results with DIY paint kits for refinishing tubs. The DIY kits are not bad, if you can avoid brush marks, but nowhere near the almost new quality and durability of a professional refinisher.
If you are looking to hire a tub refinishing company, be sure to get references from them and check out the references to see if the job they did is exactly the same type of tub as yours, and did it last. That is the best way to find out if you are talking to a reputable company or not.