Bondo should NEVER be on top of anything but 32-grit prepped bare metal, if you want it to stick and last. You can, however, use glazing putty on top of primer sanded with 80-grit. Hope this helps!
You can't paint directly over etch primer. You need a surfacer or other primer/sealer over it.
Body filler is finished with P120 grit and blown clean. All bare metal areas are covered with epoxy primer. VP2100 Polyester Primer should not be applied over bare metal, only over epoxy primer, fiberglass, or body fillers.
You can use glaze putty over primer. Either pin holes or lows or something that pops up after it's been primed on occasion. Let me give you one hint to help you, and you may be doing this, but use a Guide Coat in your body filler stages.
You only want to mix what you can use in about 10 minutes. Properly mixed, body filler will begin to thicken in 10-15 minutes, and be fully cured in 30.
filler lasts a long time, at least for me. If it is a few months old it should be fine. just mix it up real well.
Clean and sand or scuff the surface to prepare it for body filler — it will not adhere to smooth, dirty or oily surfaces. Generally, if paint will stick, so will Bondo. Conversely, if there's an area you don't want Bondo to stick to, apply a release agent (see tools and materials) or use Scotch tape or wax paper.
The Best Car Body Filler
- 3M Bondo 261 Lightweight Filler. See More Reviews.
- Permatex 25909 Liquid Metal Filler. See More Reviews.
- 3M Bondo Professional Gold Filler. See More Reviews.
- Evercoat 156 Light Weight Body Filler.
- 3M Dynatron 492 DynaLite Lightweight Body Filler.
- Evercoat 112 Rage Gold Premium Car Body Filler.
What you are working with needs to be properly prepped BEFORE you apply any body filler. Do not slap Bondo onto a smooth painted surface, it is not going to stick very well. The paint should be sanded off, to the bare metal, and then apply the filler. A 36-grit to 180-grit surface is ideal for body filler application.
There is no minimum thickness for Bondo, but there is absolutely a maximum. You do not want to apply body filler to anything that is thicker than about a 1/4”. That does not mean it can't be done, but the repair will not last as long.
Epoxy primer refers to sealer that is a non-porous finish. It is primarily recommended as the first base coat over bare steel. These base coats or epoxy primers can be used over fiberglass, plastic or the black iron phosphate coating.
Bondo Fiberglass Resin is designed for repairing cars, boats, snowmobiles, jet skis, bathtubs and showers. Bondo Fiberglass Resin is waterproof and is compatible with all paints, including gel coat and marine paints.
The trick with High build primers is to keep the application to 3 coats at a time. I will usually go 3 applications of three coats. Finish the body work with 180 grit sandpaper and get all of your pinholes and sandscratches filled before you prime.
Self-Etching Primer
But a key difference with etch primer is that you need to apply your filler or bondo first directly to the metal before spraying it.While polyester primers are great for filling, they can be porous. Once you're finished sanding the polyester primer, use a urethane primer or a sealer over it. Urethane primers are a better surface for basecoats. The urethane primer is much denser and seals the polyester surface.
The short answer is filler companies suggest it needs to go on bare metal, and epoxy companies suggest you put filler over epoxy so they can sell more of their product.
A better quality (thicker) drywall primer or a "hiding paint" will cover them up completely. Porosity is equalized. Drywall primer soaks into paper, scuffed paper, and mud—the areas of differing porosity—and creates a uniform surface to which the finish paint can adhere.
I would rather fix and bondo all of the spots, and then top coat them off with some 2k at once. Vs setting up, and painting 6-7 times. Between life and work, the longest time period the bondo would go Unpainted would be about 2-3 weeks.
Using wood filler before painting is a quick and easy job.
- Step One - Sand Holes. A nail or screw hole has to be tidied before filler can be applied.
- Step Two - Apply Filler. Get a paste-base wood filler and apply it in the neatened hole.
- Step Three - Sand Filler.
- Step Four - Clean.
- Step Five - Check.
Clean and sand or scuff the surface to prepare it for body filler — it will not adhere to smooth, dirty or oily surfaces. Generally, if paint will stick, so will Bondo. Fully cured Bondo is harder than soft pine, and is not flexible.
Yeah, that's totally normal. It's just that the patches of bondo soak up the primer differently than the metal but epoxy is the way to go. Just let it dry and give the entire truck a light sand with 400 grit and apply a couple more coats of epoxy.
