Hi Jim,
What Geoff and Mark have said so far is good advice. As i see it, basically you have two major options here to choose from. The first option is to keep on persevering with trying to remedy and repair your existing spoiler.The second is to cut your losses, and buy a new fiberglass spoiler and refinish it to your liking. There are arguments for both options, and you will have to decide which one is best for you. It really comes down to a money thing here.
You have been faced with a blistering or bubble problem on your fiberglass spoiler. That is a fairly common problem with fiberglass itself. Fiberglass can be a ***** of a material, and play up badly sometimes.This can be from moisture probs or gel coat pobs. I won't get technical here. You say that you have made 3 attempts yourself to try and fix the problem, and your paint shop has had a go once but failed as well to fix the problem as it keeps on coming back. When you look at that from a labor and materials perspective, eg, a cost perspective, i'm sure that you have thrown a fair bit of money trying to rectify this problem.
But the overall news is not good for you, because the reality is, that you can try and have another attempt at fixing this problem, throw even more money at it, but unfortunately, there will be no guarantee that the problem will not come back again. The initial cost to buy the spoiler, plus all this extra money you are putting into it, gets out of hand. On that basis, sometimes it pays just to cut your losses and start again with a new, good quality fiberglass spoiler, and refinish it to your own taste.
I can give you technical advice on trying to fix your blistering problem, but i can't guarantee that will completely solve your problem, and the blisters will never come back. The basic tech advice is as follows. First up, you don't mix two pack paints with acrylic lacquer paints, or to be more specific, you can't put two pack paints over lacquer paints. What paints have you been using so far to try and fix the spoiler? Also, have you or your spray shop attempted to back gouge out where the bubbles are, and back fill in the holes or depressions left behind?
My attack on the bubbles would be to first, sand down to the fiberglass level around the bubble areas. Next carve or gouge out the fiberglass bubbles well into the glass layer. Next, and with the glass being super dry, spray two or three good coats of epoxy primer on those spots and surrounding raw fiberglass areas. This seals the fiberglass surface off, and gives you a good sound base to work from here. Next, scuff dry the epoxy primer, and back fill in the holes with a two pack wiping putty. I would choose a product that has aluminium mixed in with the putty. This type of product is used for repairing metal rust holes, and cures out very hard. Sand the filler down level, and apply another two coats of epoxy primer over the repair spot areas. Lightly scuff down that primer dry, and then prepare the rest of the spoiler for priming the whole thing with three or four coats of standard 2 pack urethane primer/ filler. Sand that down when cured, and then move into your top black color coats. You can choose to use a 2 Pack mat or satin black paint here, or you can use a mat or satin black acrylic lacquer as an option. I like using a lacquer, as i don't end up getting any nibs in the paint finish at the end. With lacquer, i can remove all nibs on the fly, and get a nib free finish - with 2 pack, you can't do that.
Remember, if you have lacquer black paint on your spoiler now to start off with, you can't apply any 2pack or epoxy paints over the lacquer paint. If you need any more detailed tech info, PM me.
Hope all that helps make up your mind on which way you want to go.
Thanks,
Greg.
