Surfacer and Primer / Sealer Questions for Urethane Base and Clear

[32J]

Hi Folks,

For my MKIV, my initial bodywork using Rage Gold for the seams is done. I think I'll need another layer in a few spots, as I can still feel some waves. Note: I have not blocked any of the non-seam areas (hood, trunk lid, cowing, doors, etc.). Just wondering how important this step might be? Can't see any waves with my untrained eye. I turned the lights out in the garage and used a flashlight, and couldn't see anything on the gelcoat that was obvious.

I'm planning on a 2-part paint: Urethane base and clear. I've read quite a few posts on bodywork, but I'm left with a few questions that I'm hoping someone can help me with (my questions are more about product selection, and not the intermediate sanding that may be needed):

1) There are some pinholes in the Rage Gold filler, and a few blemishes / nicks / pin holes in the gel coat. Is it better to use a glaze on the specific areas only, like USC Icing, OR, a full-body polyester surfacer like Eastwood Slick Sand or Featherfill? (I've read that Featherfill has less build-up, but shorter pot time. I'm worried about the surfacer adding too much thickness to the gaps for doors, trunk, and hood.

2) If using Slick Sand or Featherfill, do I need to apply a sealer BEFORE the primer? I think I do, to prevent the primer from soaking into the Slick Sand /Featherfill. Or, should I just allow for 3 coats of primer?

3) If I use Icing glaze to spot treat the filler pinholes and gelcoat blemishes, not sure if I will then need a sealer (such as an acrylic urethane), or if the eventual epoxy primer will do the trick to prevent the base coat from absorbing into the filler. Suggestions?

4) I read that an "adhesion promoter" may also be needed for the hood scoop, because it's plastic and not as rigid as the fiberglass. Is adhesion promoter only needed for the hood scoop, before the primer?


Thanks in advance for the helpful advice!

32J

20220815_123029.jpg

[Chris347]

I’ll try to answer a few of your questions about products without getting too detailed about blocking etc. I would try to repair as many imperfections to can find with a quality filler like Rage gold. Once you have the body where you “like” it, Apply slick sand over the entire body, block sand and reapply slick sand. You will still find pinholes which you can fill with leftover SS from the cup with toothpick. I used very little glaze in the process but when I did stuck with a 2part product also from Evercoat. The purpose of a sealer is to seal in any exposed filler, and primer to provide an even base before you spray your BC/CC. The sealer also allows the BC/CC to bond properly to previous primer and fillers below. When I did my scoop I lightly scuffed it sprayed adhesion promoter and then primer as it is ABS. Hope I helped answer some of your questions.

[32J]

I’ll try to answer a few of your questions about products without getting too detailed about blocking etc. I would try to repair as many imperfections to can find with a quality filler like Rage gold. Once you have the body where you “like” it, Apply slick sand over the entire body, block sand and reapply slick sand. You will still find pinholes which you can fill with leftover SS from the cup with toothpick. I used very little glaze in the process but when I did stuck with a 2part product also from Evercoat. The purpose of a sealer is to seal in any exposed filler, and primer to provide an even base before you spray your BC/CC. The sealer also allows the BC/CC to bond properly to previous primer and fillers below. When I did my scoop I lightly scuffed it sprayed adhesion promoter and then primer as it is ABS. Hope I helped answer some of your questions.

Thanks for that. I suppose some of my questions come from that some threads seem to use some terms interchangeably (? maybe it's just me). Is Slick Sand or Featherfill considered the "sealer" when people mention in various posts? My understanding is that Slick Sand or Featherfill is a "surfacer" and not a sealer. Do most DIYs for bodywork apply sealer and primer as separate products, or would an "epoxy primer" accomplish both sealing exposed filler (and the Slick Sand / Featherfill), and and serve as primer for base coat?

Thanks for helping me out! I'm a bit on information overload from reading all the various threads on the subject.

[Jeff Kleiner]

Hi Folks,

For my MKIV, my initial bodywork using Rage Gold for the seams is done. I think I'll need another layer in a few spots, as I can still feel some waves. Note: I have not blocked any of the non-seam areas (hood, trunk lid, cowing, doors, etc.). Just wondering how important this step might be? Can't see any waves with my untrained eye. I turned the lights out in the garage and used a flashlight, and couldn't see anything on the gelcoat that was obvious.

I'm planning on a 2-part paint: Urethane base and clear. I've read quite a few posts on bodywork, but I'm left with a few questions that I'm hoping someone can help me with (my questions are more about product selection, and not the intermediate sanding that may be needed):

1) There are some pinholes in the Rage Gold filler, and a few blemishes / nicks / pin holes in the gel coat. Is it better to use a glaze on the specific areas only, like USC Icing, OR, a full-body polyester surfacer like Eastwood Slick Sand or Featherfill? (I've read that Featherfill has less build-up, but shorter pot time. I'm worried about the surfacer adding too much thickness to the gaps for doors, trunk, and hood.

2) If using Slick Sand or Featherfill, do I need to apply a sealer BEFORE the primer? I think I do, to prevent the primer from soaking into the Slick Sand /Featherfill. Or, should I just allow for 3 coats of primer?

3) If I use Icing glaze to spot treat the filler pinholes and gelcoat blemishes, not sure if I will then need a sealer (such as an acrylic urethane), or if the eventual epoxy primer will do the trick to prevent the base coat from absorbing into the filler. Suggestions?

4) I read that an "adhesion promoter" may also be needed for the hood scoop, because it's plastic and not as rigid as the fiberglass. Is adhesion promoter only needed for the hood scoop, before the primer?


Thanks in advance for the helpful advice!

32J

20220815_123029.jpg

Many times terms are interchanged or used incorrectly. From bottom to top the progression is Polyester high build primer (Slick Sand, Featherfill and the like)...2K Catalyzed primer surfacer and 2K catalyzed sealer. Some skip the sealer but I don't advise it...think of it as insurance serving as a barrier against contamination from anything below the paint. Notice that I didn't mention epoxy; although it can be used on our cars it's primarily for metal.

Body and panels need to be blocked with 80. The gelcoat actually serves as a pretty good guidecoat to reveal highs and lows as you're going over it with the 80. You'll probably find lots of ripples around the perimiter of the hood, trunk lid and doors due to the heat generated by the adhesive used to bond the inner and outer layers and quite frequently orange peel in the gelcoat.

My recipe:

I use Rage Gold for the major bodywork. After Rage I like to put down a thin skim of 3M Platinum Plus filler like a glaze to slick it off. The Platinum Plus works well for pinholes that will inevitably show themselves after the Polyester has been put down.
After all body preparation (more on that in a minute) apply 2 gallons of Polyester high build (Evercoat Slick Sand is my product of choice). Block smooth with 150 and make any bodywork corrections necessary, fill pin holes, etc. Next apply 3 coats (1 to 1.5 gallons) of 2K catalyzed Urethane Primer Surfacer (I use PPG Shopline JP202). Block smooth with 320 dry followed by 600 wet. Following this apply 1 full coat of catalyzed Urethane sealer (I use Shopline JP335 or 337 or a cocktail of both depending on the paint's undercoat color requirement). Nib sand with 1000 as necessary then move immediately to base and clear. I said immediately because if it isn't covered with the base color within 48-72 hours you'll lose the chemical bond which can result in adhesion problems.

Earlier I said "more about bodywork". As things things stand in your photo you are not ready to start putting down the Polyester yet. You'll have lots more filler going on once you start fitting and shaping doors hood and trunk. Something like this:



Regarding adhesion promoters on the ABS scoop. Sometimes a product such as Bulldog is used but I have had good luck by relying on a sharp tooth and mechanical bond by giving them the same 80 grit/polyester/2k urethane/sealer prep as the body.

Hope some of that helps!

Jeff

[cc2Arider]

Awesome summary Jeff! I appreciate your willingness to repeat your recommendations (as often as needed)

Craig C

[32J]

I think ALL of that helps. Thank you, Sir!

All I need now is more time and money.

32J

[j.miller]

God bless you Capt.-O-Ring......I Hydrolocked (Rum locked would be more accurate) on where to start with this one...da Batl