Wetting by the solder alloy is crucial to ensuring the strength of a joint for a particular application. The main reasons for poor wetting are surface contamination of the materials to be joined, inherent poor solderability (some materials wet faster and to a greater degree than others with the same alloy/flux system, e.g. a gold finish may give better faster wetting than nickel/palladium), or insufficient heat applied to the joint. Cleaning with a solvent wipe is the easiest way to remove grease and general dirt from a surface. The flux used with the solder will also have a cleaning effect, particularly on surface oxides and hence a stronger flux may give better wetting. Pre-tinning the surfaces will help in ensuring the process is more reliable and will give an indication if one particular surface has poor solderability. The application of sufficient heat to the joint is important to ensure the solder is fully molten. The use of flux as a heat transport agent speeds up the soldering process, especially when reworking an existing joint. The use of extra flux, in addition to that present in a cored wire or on a preform, should be considered especially where the joint geometry makes it difficult to heat the whole joint area at once. The tip size and shape of the iron as well as temperature can also be adjusted in order to get enough heat to the joint.