The pictures below detail common causes of weld defects.

The weld was started correctly but completed too quickly. No wash indicates haste or too low a temperature.

The hot-air tool was not allowed to attain the correct operating temperature and the weld was finished too soon, leaving a hole.

Too much pressure has been applied to the rod leaving a low and deformed bead. Filling may be necessary.

The welding temperature was too high, blistering the sides of the weld. The repair area may be brittle.

Welding Defects and Causes

Poor weld penetration or poor bonding	--Incorrect weld site preparation --Weld speed too fast/temperature too low --Weld attempted with dissimilar materials --Poor technique
Uneven weld bead width Charred weld	--Welding rod stretched --Uneven pressure applied to welding rod --Welding speed too slow --Temperature too high
Warping	--Repair area overheated --Parts fixed under tension --Poor site preparation