I recently did a hood scoop a month or 2 ago and now I am getting these random bubbles on the fiberglass and they are hallow like air pockets developed. My mixture was right It wasn't cold when I put it on there and I cleaned my surfaces and scored them to get a good bond. I have never had this problem before with speaker boxes, panel repair, rust repair, and numerous different things but this has never happened to me so what is it?

The biggest mistake most people here make is that they tend to use the resin/fiberglass stuff that Auto Zone or Walmart sell to bond and fill the work which in my honest opinion is going to cause problems anyway. It tends to shrink after it gets painted and make all the hard work of prepping and finishing a waste of effort.

Did you use fiber glass reinforced bondo for the build up after bonding the hood scoop?

I use Lord EZ100 SMC fusor a 2 part epoxy to bond, fiberglass reinforced bondo for the build and then Evercoat polyester putty to put a finish glaze over that before final sanding and priming. Just finished painting it but my hood sat for 3 months before I got around to that and no problems with bubbles.

Bottom line when using fillers and paint and epoxies there are so many variables that who knows what caused it. You could have looked at the resin container wrong one day. Bubbles usually is trapped air or off-gassing from your resin(s) or paint. There is a saying in my line of work however. " I do it nice because I do it twice."

quote Originally posted by Curlrup: " I do it nice because I do it twice."

Try three or four times. Good luck

Buddy of mine is a licensed paint/body dude. For like 25 years. Even teaches it at a local college (just saying - he knows his stuff!).

Painted another buddies Fiero after it had a custom hood scoop done... guess what... little tiny air pockets a few months after!
And to think he gave ME crap when... you guessed it... I did a scoop on my front hood and painted it.... and got air pockets a month or so later!

I did mine in the heat of summer - he did his in the winter'ish time.

The other job's he'd done on other Fieros? All stock. No flaws.

I'm seeing a connection here though. Paint doesn't like hood scoops.
Ok - maybe it's more likely the filler being used. I'm betting it's the putty though.
I think someone already mentioned outgassing?

Next time I do something like that, I'm going to spray with a good sealer coat first. And cross my fingers. Tight.

The most important thing to remember when working with SMC is that you're working with SMC. You need to always use materials *made* for it. It has a release agent made into it. If the materials are not *made* for SMC, they won't stick very well. That & the obvious: make sure there are no air pockets when you spread the material. Work it into the surface well. I always grind with 24 grit too, before bonding &/or filling anything (unless I'm bondoing over epoxy primer, which does not apply when installing a hood scoop or repairing fiberglass).
HTH,
~ Paul
aka "Tha Driver"

America - made in China! :-(

If I understand what you are describing, it's called blisters in the boat world. they are voids that form between the topcoat, which is gelcoat, a colored resin and the glass itself. it is a royal PITA, and from what I've read and seen myself it is from insufficient resin used when laying the fiberglass up, so there are dry spots. dry = no stick together, and air trapped under the finish coat, whatever that may be. there is only one way to fix it, grind out the area and re- epoxy it. when laying up fiberglass, I use alot of resin/epoxy depending on where it being used. while similar, they are not the same. resin is a top coating, epoxy is used for structural components. depending on the size of the piece I will soak it in a pan full of resin before laying it out, but if a larger piece , will start with a liberal base of epoxy, cloth/mat and a soaking layer of epoxy. I use a stiff cheapo chip brush to stab the glass working from the center out, or if la large piece as I lay it down to force out all the air. Works very well, but time consuming.
There is no "outgassing" in epoxy or resin, unless you aerated it while mixing it up, a definate no-no.
If the glass piece is properly constructed, then all the is left is to use the proper bonding agent to the hood. that part I'll leave to the body guys here, I haven't worked with smc. I have done alot of fiberglass work in various boats I;ve owned, and never had a failure or blistering, even re-glassing the bottom of an old skiff I had, and working out 13'x4' matt on an uneven surface on a warm summer day is NO picnic. Saturation is your friend with fiberglass. then a good sander to get rid of the excess. I would much rather sand off blobs that see bare glass, as that means possibly sanding thru the glass to clean below it . most epoxy and resin form a wax on the top as it cures, and that MUST be removed for any proper adhesion. non waxing resin/epoxy is available, but is not that common and you specifically have to ask for it. a good scrubbing with acetone will work also, but will not rough up a surface well enough to adhere more glass/paint/adhesive.

quote Originally posted by tjm4fun: There is no "outgassing" in epoxy or resin

Just to clarify, I was referring to the filler - i.e. bondo, or the surface glaze possibly used.
Surface glaze putty is laquer (or similar) based and air dries through solvent evaporation.

When I did my deck scoop, it is a molded fiberglass scoop. I used SMC Panel Adhesive to fill and smooth. I then used the standard Auto Glaze for the finer finish. No bubbles. I expect that the fiberglass resin has to be thoroughly cured before you try SMC. I'm not sure how long fiberglass resin continues to cure, but I expect it is at least a week, and if the mix isn't bang on, probably longer.

I sanded and filed mine down to as good a fit as I could get, and then the SMC. That sanding took off the outside surface pretty well all around the rim to be bonded. The guys who made the scoop are pros so their mix was likely good and it was old enough to not retain fumes.

Hope this helps.

Arn

What Driver said. You have to use similar materials. I always see guy putting fiberglass scoops on metal hoods and I guarantee that NEVER works. Soon as the hood and scoop have gone thru some heat cycles, its on its way to destruction. If you must use different stuff, you have to make sure the filler, resin or whatever is compatible with both and then cross your fingers. Keep the depth of fillers to the minimum....thicker it is, worse luck. Also remember some primers soak up moisture, so if you prime your body work and leave it for months before paint, you may also have bubbles or cracks appear when you do paint it if not before.

quote Originally posted by watts: Just to clarify, I was referring to the filler - i.e. bondo, or the surface glaze possibly used. Surface glaze putty is laquer (or similar) based and air dries through solvent evaporation.

Never, I repeat NEVER, use an air dry glazing putty! It's made for pinholes & scratches ONLY, & that was a *few* decades ago. Now we have better materials: I never use anything that is not catalyst-hardened.
~ Paul
aka "Tha Driver"

Pardon my driving; I'm reloading.

ok as far as the weather when I made it was warm 80ish and I think the problem was one of the nights when it was cureing we had a cold snap. I took my sander to the bubbles and found some in the filler and some in the fiberglass. But now with the warmer weather I am going to redo it all any tips because I scored the surface with a wire wheel before bonding and cleaned everything so I will see if I can do it alot better.

Wire wheel is the last thing you want to use. Find a grinder of some type that you can use 24 grit discs on. Also, re-read the above posts: use ONLY materials made for SMC.
~ Paul
aka "Tha Driver"

I checked today and... this is the oldest I've ever been.