It is recommended that parts are degreased prior to welding as the oil will burn into the material and cause brown discolouration after cleaning the weld. It is important not to include any black iron, as this will be dissolved by the acid.

When items are delivered to Kd-bejds, they must be ready for pickling. If you want a cosmetically pleasing result, the following is important:

All items must be degreased to remove oil, grease, foil glue and the like, otherwise the stain will not penetrate.
Please note that some paints do not dissolve when stained.

Residues of oil or glue are usually only visible after staining and cannot be repaired, and staining will not remove scratches or other marks in the steel.

The picture shows oil burning and ink that does not dissolve in the acid.