Body Filler, Bog and Spot Putty for Panel Repairs

Every panel repair that ends in a straight, flat finish started with the right filler and enough patience to sand it properly. Affordable Paint Supplies stocks body filler, fibreglass and plastic fillers, spot putty, glaze, hardeners and applicators for panel shops, restorers, smash repairers and home workshops. If you’ve always called it bog, you are in the right place - bog filler and body filler are the same thing. You’ll also find the abrasives, fibreglass repair products and primer aerosols that go with the job.

What Body Filler Actually Does

Body filler restores shape… it doesn’t restore strength.

Car body filler is a polyester resin paste mixed with a cream hardener. Once catalysed it cures chemically rather than drying, which is why it goes off far faster on a warm day than in a cold shed. You apply it slightly proud of the panel and sand it back to the original body line.

What auto body filler won’t do is hold a panel together, bridge a gap, or fix rust. Bog over rust hides the problem for a season and then lifts as the corrosion keeps working underneath. Cut the rust out, weld or replace, then fill.

Polyester filler is a cosmetic product used at the end of the metalwork, not instead of it.

Filler, Putty or Glaze - Which One and When?

Match the product to the depth of the repair.

• Heavy-build and universal polyester fillers handle dents and the bulk of a repair. Master Universal Polyester Filler and 3M Platinum Body Filler both sit here, and lightweight fillers sand more easily over larger areas.
• Reinforced and fibreglass filler is for repairs that need strength or moisture resistance, such as around a repair patch or on a boat or caravan panel. U-POL Fine Metal Polyester Paste is the metal-reinforced option in our range.
• Plastic body filler flexes with the panel. Isopon Plastic Bumper Filler and Master Plastic Polyester Body Filler are made for bumpers and flexible trim, where a rigid automotive body filler would crack the first time the panel took a knock.
• Spot putty and glaze are finishing products only. Everglaze Spot Putty, U-POL Dolphin Glaze and Evercoat EasySand fill pinholes and sand scratches ahead of primer. Used over a deep dent they will shrink and sink, and the repair will telegraph through months later.

Mixing Filler and Hardener

Follow the ratio on the tin, not a rule of thumb.

Body filler hardener ratios vary by brand, by product and with ambient temperature, and every manufacturer prints its own on the packaging or the technical data sheet. Read it. A guess that works for one filler will not carry to the next.

Too much hardener and you get pinholes, staining that bleeds through your topcoat, and a mix that goes off before you have finished spreading it. Too little and it stays soft, clogs your paper and never sands clean.

Mix on a clean board with a flat spreader, folding the hardener through rather than stirring it. Stirring whips air in, and every bubble becomes a pinhole you will chase later with putty.

Bare Metal, Primer or Plastic

Whatever you are filling over needs to be clean, keyed, dry and free of rust. Bare, sanded metal is the ideal substrate. Filler grips mechanically into the sanding scratches, so a coarse key gives it something to hold onto. Applying over cured epoxy or 2K primer is fine where the filler's technical data sheet allows it, and many do. Never apply over bare rust, wax, grease or silicone.

Plastics need a flexible filler and usually an adhesion promoter first. Degrease before you sand, not after, or you’ll drive contamination into the surface. Our paint prep range covers degreasers and wipes.

Sanding - Timing and Grit

Sand it green, not rock hard. There’s a window after the filler kicks where it cuts easily and still shapes well. Leave it overnight in a cold shed and you will fight it with every sheet. How long that window lasts depends on temperature, how much hardener went in and which product you are using, so watch the repair rather than the clock.

Start coarse to shape, move up to refine, then feather the edge into the surrounding paint, and finish finer again before primer. Use a block or a file on flat panels. Sanding with your fingertips puts a row of shallow hollows into the surface, and you will see every one once the light hits the finished paint. Blocks, files and paper are in the abrasives collection.

Brands the Trade Knows

We stock automotive body filler from Master, 3M, U-POL, Evercoat, Isopon and Roberlo, along with the hardeners, applicators and mixing boards that go with them. Trade pack sizes are available, and if you buy filler by the drum, ask about bulk pricing.

Not sure which filler you need?

Tell us the panel, how deep the damage runs and what the substrate is, and we will match you to a filler that suits it rather than one that happens to be on the shelf.

Frequently Asked Questions

Q: What is body filler (bog) used for?

A: Body filler, or bog, restores the shape of a panel once dents, creases or minor damage have been worked out of the metal. It is a polyester paste that cures chemically, applied slightly proud of the surface and sanded back flat. It is cosmetic - it adds no strength and does not repair rust.

Q: What's the difference between body filler, spot putty and glaze?

A: Body filler builds. It fills dents and shapes panels and can be applied several millimetres thick. Spot putty and glaze are finishing products for pinholes and sand scratches, applied as a thin skim ahead of primer. Use putty over a deep dent and it will shrink and sink as it cures.

Q: How much hardener do you mix with body filler?

A: Use the ratio printed on the product. It varies by brand, filler type and temperature, so there is no universal figure worth quoting. Too much hardener causes pinholes, bleed-through staining and a mix that goes off before you can spread it. Too little leaves filler that never cures hard enough to sand cleanly.

Q: Can you apply body filler over bare metal or primer?

A: Both work. Bare, coarsely sanded metal is preferred, because filler keys mechanically into the scratch pattern. Applying over cured epoxy or 2K primer is fine where the technical data sheet permits it. Never apply filler over bare rust, wax, grease, silicone or loose paint.

Q: How long before you can sand body filler?

A: It depends on the product, how much hardener went in and how warm the workshop is, so the clock is less useful than the filler. Press a fingernail into a scrap of the mix. When it no longer marks easily but still cuts freely with coarse paper, it is ready to shape.

Q: What grit sandpaper should you use on body filler?

A: Work through the grits rather than jumping. Shape with a coarse grit on a block, refine with a medium grit, feather the edge into the surrounding paint, then finish finer again before primer. Skipping steps leaves deeper scratches that show through the topcoat.

Q: Which filler is best for deep dents vs fine finishing?

A: Deep dents want a heavy-build or universal polyester filler, applied in layers rather than one thick pass. Fine finishing wants spot putty or a glaze in a thin skim. Where the repair needs strength or moisture resistance, a fibreglass or metal-reinforced filler is the better build coat.