Small bubbles in epoxy resin??

[Boomyal]

Several times, now, I have applied epoxy both on CPES pretreated plywood and now over 10 oz cloth. As I apply the resin, it produces lots of small bubbles as if something is off gassing. When the resin cures the bubbles are still there.<br /><br />I just finished putting a layer of cloth over biaxial mat, in my bilge. I cleaned the blush off the previous coat of resin, sanded it down and wiped it with acetone. As I rolled on the resin the bubbles would appear. I kept popping the bubbles with the roller and they would show back up.<br /><br />Any ideas??

 

[Elk Chaser]

Re: Small bubbles in epoxy resin??

Generally the causes for this are either... <br />Too Much Hardener<br />OR<br />Not Enough Mixing

 

[BillP]

Re: Small bubbles in epoxy resin??

Lightweight 10oz cloth is among the worst for bubbles. Most bubbles are just air being trapped while the resin is applied. Some bubbles are from outgassing but not many...those are found mostly on casting resin where thick and hot. Others (pin size bubbles)are caused by the surface sucking resin out of the glass and leaving a dry laminate. Are you using a ridge roller to get the bubbles out after getting the resin down?<br /><br />I personally have not experienced bubbles from too much hardner or not enough mixing...for what it's worth I've mixed 1000s of gals of polyester and 100s of epoxy. My worst bubbles were when pouring polyester casting resin 1" thick on table tops. Casting resin is so thick the bubbles get suspended and don't make it to the surface for popping.

 

[Rudderman]

Re: Small bubbles in epoxy resin??

If you're working on wood, seal the wood first with a coat of epoxy applied by roller. Let it cure fully, then lightly sand it/wash it to remove any blush. Then when you apply your cloth, you should not have any outgassing from the wood. <br />Tip off the wet epoxy lightly with a foam brush or an ordinary brush, this pops any remaining tiny bubbles.<br />Maybe the biaxial mat was not totaly sealed and there was air trapped in the fibres?<br />Apart from that, the only other time I've seen bubbles form is when you move the roller too fast or use a roller saturated with epoxy that is beginning to cure.

 

[18rabbit]

Re: Small bubbles in epoxy resin??

Fwiw, I occasionally get tiny little bubbles in epoxy. It is definitely NOT from an error in mixing rations, nor is it an issue with not mixing enough...and it’s epoxy on epoxy so it’s not off-gassing, either. Don’t know what causes it. I thought I might be over mixing parts A and B before adding fillers. Noticed there is tons of bubbles suspended in the mixture that I presume get mixed in when the fillers are added. It’s never an issue unless I don’t add fillers and need to pour the epoxy, like in something BillP mentioned, except my bubbles do come to the top and harden there. After sanding I have teeny, pin holes on the surface. Have not experienced it at all with the CPES.<br /><br />Right now I am using a gal of West Systems 105B and 206B hardner.

 

[Boomyal]

Re: Small bubbles in epoxy resin??

Because I had so many planes to cover using one 43" x 39" piece of glass, I started out by laying the glass dry on the bilge floor and pouring resin on top of it. Prior to running the glass up and over the top of the motor mount stringers, I rolled and squeegied resin on to the surfaces before I rolled the glass down on them. Both surfaces seemingly bubbled equally.<br /><br />I did use a ridged roller and kept rolling it over the bubbles. With many repeated passes, I was able to reduce the number and size of bubbles that would have otherwise remained. But many times bubbles would reappear after I rolled them out. I finally gave up as the resin start to blow. <br /><br />Now that I think about it, I did not get the bubbles when I layed the biaxial mat as the first coat. <br /><br />Previously, I mixed some just pourable (thickened with cabosil), epoxy to creat a radius at the bottom of my stringers. That mix had a zillion leeeetle bubbles in it that never surfaced. You can see them below but the surface is smooth. I just took that to be from air trapped during the mix with cabosil.