Whether you are removing dried caulking from a fiberglass bathtub to repair the joint between it and the wall or removing it due to a spill, the process is the same. Use a chemical caulk remover to soften the bond.
Apply the chemical caulk remover
Apply the product from two to seven hours before attempting to remove the caulk so it has time to dissolve the bond. Be sure to cover all the caulk.
Slice the seam with a utility knife
Use a utility knife with a new blade to slice through the joint of the caulking and the tub. Be careful that you do not cut or scratch the fiberglass. Another alternative is to use a special caulk removal tool available at hardware stores. The tool has three blades to cut through the caulk in a corner, along with a hardened plastic edge to prevent scratching or cutting the tub.
Pull with needle-nosed pliers
If the caulk is resistant, grab it with needle-nosed pliers and pull. Use a plastic putty knife to remove any remaining caulk.
Eliminate any mold
Often water gets behind the caulking and mildew starts to grow. Before applying more, kill the mildew. Popular Mechanics recommends applying a solution of 1/3 cup of chlorine bleach in a gallon of water, using a paintbrush and scrubbing with a plastic brush.