Blending new paintwork into an existing finish is something paint technicians are frequently required to do. The good news is there is a recommended and proven process for achieving a consistent, successful blend. The bad news is, some technicians choose not to stick to it – whether it’s the pressure to get the job done quickly or just getting lazy, they start cutting corners. The result is dark patches, shadows or ‘profiling’ in the blend area which results in a costly rework that disrupts work scheduling and blows out cycle-time.
Tips and Recommendations
Throughout the preparation process and actually applying the blend, there are several steps which are considered absolutely critical.
Sand, don’t scour – When preparing a panel to be blended, simply rubbing it with an old scourer isn’t good enough. Why? Because the panel already has two or more layers of OE clearcoat and some of that film-build must be removed. If not, applying two more coats during the refinish process will mean you are looking through four or more layers and that causes a darkening effect. To remove some of the existing film-build from the paintwork it should be sanded with 1000 grit abrasive.
Next, it’s recommended to go over the blend panel again using a Startline P1500 Grey Scourer disc with a machine and a Startline P1500 Grey Scourer pad by hand in areas that can’t be reached by machine. This leaves a nice even scratch pattern which won’t show through the blend and result in a rework.
Tack-rag before clearcoat – At first glance, this mightn’t seem important but it is because tack-ragging removes the fine overspray dust from the surface. If it’s not, the dust particles can stand up in the film and create shadows, particularly in metallics. Note: Be sure to use a tack-rag that’s in good condition – not one that’s been in your back pocket for a week or left in the spray booth.
Two stage clearcoat application – The first layer of clearcoat should be applied up to around the door handle (around 15cm from the panel edge). The second coat goes right to the edge. If the panel has been sanded correctly, this will give us an OE-type clearcoat film build of around 50 to 55 microns and avoid the darkening effect of too much film build.