Amine Blush

[Bill A]

I have a technique question. I sometimes use chopped fibers and cabosil to make a thick, structural fillet. My problem is after the cure. The fibers stick out and make a rough surface which is difficult to scotch brite to remove the amine blush. I use System 3, and I haven't had much in the way of a film, but I always rinse anyway. My question is, has anyone sanded the fillet or epoxy first, to obtain a smooth surface, then rinsed? Or is rinsing even needed after a thorough sanding.
Thanks
-Bill

[Dave, 397]

If you sand or grind, there is no need to rinse...the blush is on the surface, and if you essentially remove that topmost surface there is no blush.

A good analogy might be to the slag that forms on the outside of the bead from stick welding...it's only the outermost surface and once chipped off you are looking at the good clean weld. Pretty much the same idea only the epoxy blush is a thinner layer by a whole lot!

Incidentally, there are no-blush type epoxies available from Progressive Polymer Products ( www.epoxyproducts.com ) , as well as a wealth of info. His website is the oldest, EZ-Bake site you can imagine (OK, maybe a close second to Rigging Only) and takes a bit of patience and fooling around to navigate...but it is worthwhile to do so!

Best,
Dave

(home puking having forgotten that Ironwood is a bit toxic, especially the smoke!)

[Tim]

Actually, grinding a blush-covered epoxy surface may not remove all the blush; the sanding might just imbed it further into the surface. Always wash first.

Using chopped fibers for fillets is not the right choice, though. As you have found, they are too rough, and require much difficult sanding. If you laminate over a rough-ish surface, you run the risk of not acheiving a good bond, as there will be myriad air pockets beneath.

For true fillets, use a filleting filler, or mix up a batch using microballoons and a small amount of cabosil to achieve the proper thickness for your fillet.

Blush is not the big deal that some folks might have one believe. A quick wash takes care of it. Note also that it doesn't tend for form in significant quantities when using mixed epoxy fillers; it's more of a problem when applying staight epoxy, such as when laminating.

Good luck!