Frequently Asked Questions About Our Abrasives

What grit sandpaper should I use for automotive prep?

That depends on the condition of the surface and where you’re up to in the repair. For removing old paint, rust or heavier surface damage, you’ll usually start with a coarser grit such as P80 to P180. For feathering paint edges, refining body filler or getting an existing finish ready for primer, P180 to P320 is a common choice. When you’re sanding primer before paint, you’ll generally move up to something finer, such as P400 to P600.

The key is to work through the grits gradually. Jumping straight from a very coarse sandpaper to a fine one can leave deep scratches behind, and they may show through the primer, paint or clear coat later. It’s always worth checking the technical data sheet for the primer or paint system you’re using, as the recommended grit can vary from one product to another.

What’s the difference between wet & dry sandpaper vs regular sandpaper?

Wet and dry sandpaper is made to handle water, so you can use it wet or dry depending on the job. When you use it wet, the water helps wash away sanding residue, keeps the paper from clogging as quickly and reduces heat (this makes wet and dry sandpaper a good option for fine finishing, removing small paint defects and preparing a surface for polishing).

Dry sanding is usually faster and is more common during the earlier stages of prep, such as removing old coatings, shaping filler or sanding primer with a machine. Wet sanding is generally saved for finer work where you want more control over the finish. Just keep in mind that not all abrasive paper is designed to be used wet. Standard paper-backed products can soften, tear or separate if water added, so check the product details first.

What grit do I use before primer, before paint and before clear coat?

The exact grit will depend on the products you’re using and the type of repair, but these ranges are a useful starting point.

• Before primer: P180 to P320 is commonly used for feathering repair edges and preparing existing paint. You may need something coarser when shaping body filler, but you’ll want to refine those deeper scratches before applying primer.
• Before paint: P400 to P600 is a common range for sanding primer before basecoat or solid colour. Some paint systems may call for a finer finish, especially with metallic colours, lighter colours or waterborne paint.
• Before clear coat: Clear coat is normally applied straight over properly flashed basecoat, but you can lightly sand base coat to remove imperfections before applying clear coat. It’s important to use a fine grit like 800-1500 and thoroughly clean the surface thoroughly with a tack cloth to remove dust and debris.

If the sandpaper’s too coarse, the scratches may show through the finish; if it’s too fine, you may not get the adhesion you need. The product technical data sheet should always be your final guide.

What are Velcro hook-and-loop sanding discs, and what sander do they suit?

Hook-and-loop sanding discs attach to a matching backing pad using a reusable fastening system, similar to Velcro. You simply press the disc into place, then peel it off when it’s time to change grits or replace it. They’re commonly used with random orbital sanders, dual-action sanders and other compatible automotive or industrial sanding machines. You’ll need to match the sanding disc size and hole pattern to the backing pad and dust-extraction setup on your sander.

For example, a 150 mm multi-hole disc should be used with a compatible 150 mm backing pad. When the holes line up properly, you’ll get better dust extraction, less clogging and more life out of the abrasive. A standard orbital sanding disc isn’t the same as an angle grinder sanding disc. Angle grinders run at much higher speeds, so you’ll need an abrasive that’s specifically made and rated for that machine.

When should I use sanding discs vs rolls vs sheets?

Each format has its place, and the best choice depends on the size, shape and stage of the job.

• Sanding discs are best for larger areas and repetitive machine sanding. They’re commonly used for paint removal, refining body filler, sanding primer and general panel preparation.
• A sandpaper roll is handy when you want to cut your own length. Rolls work well with sanding blocks, long boards and file boards, making them a practical choice for levelling filler and sanding larger repair areas.
• Abrasive sheets are a good option for hand sanding, smaller repairs, edges, corners and detailed work. You can also cut full sheets down to suit different sanding blocks.

Where possible, use a sanding block rather than sanding with your fingertips. It spreads the pressure more evenly and helps prevent grooves, finger marks and uneven spots in the surface.

What grit removes scratches before polishing?

That depends on how deep the scratch is and whether it’s still within the clear coat. For light surface marks, dust nibs or minor orange peel, fine wet and dry sandpaper such as P1500, P2000, P2500 or P3000 may be used before machine polishing. It’s always better to start with the least aggressive grit that’ll do the job, so you don’t remove more clear coat than necessary.

Once the defect’s been levelled, work through progressively finer grits before polishing. A P1500 sanding mark will take more compounding to remove than a P3000 mark, so finishing finer can save time and make the polishing stage easier. If the scratch has gone through the clear coat and into the colour coat, primer or substrate, sanding and polishing won’t usually fix it. At that point, the area may need to be repainted.

Take extra care around panel edges, body lines and raised areas, as the clear coat’s often thinner there. When you’re unsure, it’s safer to get advice before you start sanding.