I've been learning as I go with the bodywork on my 65 coupe. I've been using the Bondo brand resin with great results but the tacky surface added a lot of time when sanding. So I bought some waxed resin from a local Fiberglass shop. My thinking was its fresher, a lot cheaper and the wax would make finishing much easier. At first I had some issues with it hardening. It required more mekp then the Bondo brand. After a few test batches I got that sorted out. Now the issue is when the area has hardened it has what appears to be large air bubbles. I tap the air out while working with the brush and finish up with a roller. This resin is much thinner then the Bondo brand. It's almost like the resin is to thin and not sticky enough to hold everything together until it dries. Thus the air bubbles. Any advice?

Thanks,
Kris

 

Not being able to watch you laminate..and not knowing how many layers you are trying to laminate up in a laminating session...and not knowing exactly what type of 'new resin' you are using....it is hard to advise you.

If the viscosity of the 'new' resin is like water....it may require a different process when laminating. I do not the resin in front of me to see how it reacts...but I have used 'tooling resin' many times and it is very thin...so it soaks into the fibers of the mat faster....and I have never had an issue with air bubbles.

I do not know how fast the resin is curing and hardening due to your activation ratio currently.

DUB

 

Thanks. I understand there are a lot of unknowns here. The resin is almost like water. I asked for and assumed I received a general purpose waxed ortho polyester resin. I am using enough mepk so that it starts to gel in my container after 20 to 25 minutes. The laminate is still tacky at this time but is rock hard when I come back the next day.
I am doing a 4 to 5 layer laminate with 1.5 ounce chopped strand mat. For repairs I v the area out and use a thin first layer and progressively wider layers. I apply the resin lightly to the repair then add the mat, wet it out and proceed with the next layer. I only use enough resin to saturate the mat. As I go I dab the mat with the brush to drive out air and use the roller every couple of layers.
The thin resin is great to work with but when I come back the next day to sand it down there are small pockets that have no resin. I assume they are air bubbles.
Does this give you enough information? I never had this issue with the bondo brand but I hated sanding trough the first tacky layer!

 

Like DUB said, a lot of unknowns here. Lets start with the basics, find out if the manufacture has a date on the product and call them if you need to and interpret it. If its in date, has it been frozen or store incorrect by you or the supplier? What is you shop temperature? Are you mixing to the manufactures specs?

These are a few basics I would start with.
Kevin

 

OK...I am assuming...after reading what you wrote above... that you are adding the MEKP to what you 'feel' is correct. And NOT actually adding 2% of MEKP to your volume of resin. Although adding MEKP can be altered somewhat....there is a specific amount that should be added....SO...all of your lamination's are consistent! Even Grandma measures out flour and all the other ingredients to make her cookies correctly.

I want my laminations to take 24 hours to harden...if yours are...then that is good. Because I do know that a large volume of activated resin in a bucket will harden much faster than what has been applied due to internal heat building up in the resin...thus making it 'kick off' faster.

No way of telling unless you grind in these 'problem areas' and respond back. It also depends on where the 'air pockets' are located...and it also depends on other variables when you were laminating. 1-1/2 ounce mat SOMETIMES needs to be 'worked' manually by hand IF the area that is being laminated raises concern for a possible LIFT of the mat. 1-1/2 ounce mat DOES have a starchiness to it...that can effect laminating. There are trick to what to do with the mat before it is applied.

Changing your resin is up to you, AND IF the 'Bondo" brand resin was tacky...and it is a laminating resin.....then to stop the tackiness....you would need to apply PVA on your lamination when competed to NOT allow air to get to the resin so it would cure up and NOT be tacky.

****** PROFESSIONAL OPINION*********
Keep this in mind.....just because it is a polyester resin does not mean that is is the best resin to use in an area. I would NOT use a 'tooling resin' for a structural repair. But that is just me. It is 'kinda like'....mortar and concrete. They are basically very similar...but I would not build Hoover Dam out of mortar. The properties of the resin is where it is at.

DUB

 

Thanks for the info Dub. I haven't had much more to contribute since I have not been able to get back over to the car lately. I can add a bit more info though,

I totally agree about using general ortho resin. I know some like the tooling resin or even the epoxy but my thinking is that the repair should try to match the surrounding area to prevent showing up later. I'm sure GM used neither of these.

I did accurately measure my resin to hardener ratio at one time and vary little from this. This doesn't mean that the new resin is the same so I have stolen the digital kitchen scale to revisit this.

Odd thing is... I bought some more 3m resin and it is much thicker then the last ones. And.... it has been drying without the surface being tacky. Great except I now have a gallon of the new resin!

You did mention at some time that there were some tricks for working with thin resins. Could you elaborate? I plan to check my resin to hardener ratio and try some test laminations.

Kris

 

I almost forgot,
I have ground into some of the past laminations and the areas I'm seeing definitely seem to be air bubbles. They appear white and as I grind down there is no resin there. They are not there at the end of the laminating process but appear when I go back the following day. I need to do a test lamination early in the morning so I can check on it during the day.

 

Other than reading what you wrote in the last two posts...I do not know what to comment on.

I do not know why you are getting air bubbles in your cured resin... if you are certain they are not here when you are done laminating. I never have had that happen to ...other that PURPOSELY accelerating the resin to show the guys I trained what would happen if they did not follow my instructions and improperly active the resin and laminate too many layers at one session.

DUB

 

i use a roller to work glass. brushes just dont work as well .

 

'Porchdog'...in the first post he wrote that he is using a roller.

DUB