Sealer under dye under epoxy

[bartek]

I'm about to start staining. My teardrop is skinned with birch plywood, and I'm going for lightish brown color and a woody finish.
I was planning to use trans tint dyes, since they seem to have a good epoxy compatibility. Trans tint seems to recommend sealing the wood first with thinned water based finish to avoid blotching.

I can't find any information whether this will cause problems with subsequent coats of epoxy.
Anyone knows or has tried? I did some small samples and blotching doesn't seem to bad so I'm thinking maybe it's best to skip the sealer altogether, but I'm also worried blotching may be more evident on a larger surface...

[Pmullen503]

If you are using glass cloth and epoxy I would not worry. Slightly less penetration due to the sealer won't matter. Water based finishes should be compatible and I've used Trans tint dyes to tint the epoxy itself.

If you just plan to coat the stained wood, I would do a test piece. You should do a test anyway to check for color.

[tony.latham]

I'm wondering if the sealer would preclude the epoxy from saturating into the wood? I'm scratching my head and leaning toward the theory that it would work fine.



As you've already observed, dyed birch isn't real blotchy... but I'm not the guy getting ready to do a full wall, either.


Looking forward to watching your build come together,

Tony

[Pmullen503]

The sealer is there to minimize the difference in dye uptake between end grain and side grain so you don't want to completely seal the wood. That's what makes figured wood figured. So a test is in order if you don't have a lot of experience with that combination of wood and finishes. You may decided you don't need sealer at all. You may want lots if you are going for a very uniform color and to minimize grain.

Several applications of thinned dye is better than one concentrated coat. Spraying dye, if you are set up to do that, can give some neat effects. The epoxy will make the color pop so it can be hard to tell the final look at the dye stage.

Avoid oil based finishes or solvents and you should be fine.

As always, pay attention to construction details so water can't pool (drains and drip edges.)

[tony.latham]

The sealer is there to minimize the difference in dye uptake between end grain and side grain...

From time to time somebody writes something that knows what they are talking about. You can just feel it.

Tony

[bartek]

I did some experiments. Good news is that the sealer didn't seem to affect epoxy adhesion in any perceivable way. Bad news is that it also did little to prevent blotching (I used water based poly thinned 2:1).

In the end, I decided to go ahead and just finish without the sealer. Turned out pretty blotchy in places, but I kind of like the look and highlighted grain structure, so I guess I'll just live with it ... Not much else to do at this point anyway.

[Pmullen503]

The wood giveth and wood taketh away....

[western traveler]

I have a question regarding using the sealer prior to glassing with epoxy. Does using the sealer eliminate the need to wet out the surface prior to laying the cloth? My understanding of wetting out is to prevent the wood from drawing too much epoxy from the fabric so if the wood is sealed?
I am used to wetting out with epoxy first. Wondering if it matters..

[Pmullen503]

Laying out the cloth dry and wetting the through the cloth is how I've always done it. As I work my way along I'm checking previously wet out sections to make sure the cloth isn't starved for epoxy. Since I am usually worried about minimizing the weight on the lay up, I squeegee the cloth down to remove excess resin. On a trailer I would be less worried about a few extra ounces of resin.

Whether sealed or not keeping and eye on areas you've already done and applying more resin to "dry" areas will give a better lay up.

[bartek]

Raka manual explicitly recommends one epoxy seal coat before the fiberglass... I believe it is to prevent off-gassing and ensure good penetration of epoxy, so given the sealers seal the wood only partially I'd think it's still important?
To be honest I don't see much downside to that first coat and it worked really well for me in terms of preventing off-gassing (I didn't use the sealer though), but my experience is limited to one build which is not even finished yet, so I'll let more experienced folks comment

[Pmullen503]

Make sure to use a non-blushing epoxy for that sealer coat. Raka makes both types of hardener so use the right one. Never try to sand the blush off wood coated epoxy. Wash it off before you sand if you plan to coat or laminate cloth over it. Sanding will grind it into the wood. Don't ask me how I know!

I stand by my earlier comments about sealing being unnecessary if you are careful about starvation and squeegeeing down the cloth but precoating with a non-blushing epoxy won't hurt. It's just an extra step.

[nbcarey]

Most dyes, Trans-Tint included, are not terribly light-fast. Expect them to fade pretty quickly in UV light.

The wooden boat guys, like the guys who restore and maintain boats like mahogany Chris-Crafts and Gar-Woods, if they color the wood other than with varnish, use pigment stains, not dyes. Because life is too short to be wooding and refinishing the hull every couple of years.



From the manufacturer's FAQ, you might note the repeated used of "indoor ambient light" when speaking of UV resistance and lightfast".

https://homesteadfinishingproducts.com/ ... s/dye-faq/

"Are your dyes lightfast?

First of all, there is no concrete definition for “lightfast”. When dealing with dyes, it’s complicated because lightfastness of a particular dye is also dependent upon what it’s applied to and the concentration of the dye. What this means is that a particular dye, when applied as a solution to bare wood might have better lightfastness than the same dye, when used in a dilute concentration as a toner. That said, let’s put lightfastness into perspective.

Our Homestead dyes (TransTint Liquid Dyes & TransFast Water-soluble Dye Powders) are fade-resistant and can be expected to be reasonably lightfast when used in conditions of normal, indoor ambient light or indoor manufactured lighting conditions.

Prolonged or intermittent exposure of dyes to strong sunlight from overhead skylights or windows (like picture windows or bay windows) may fade the dye, just like it will on textiles like fabric and carpeting. You should avoid using blue, purple, and violet dye colors that are exposed to a strong source of sunlight.

All our other dye colors should perform fine in most indoor situations, however, the best performers we offer are the TransTint Dyes (except the color blue). Our TransTint metallized dyes offer the best lightfastness you can get with a dye stain. However, they are not rated for exterior use."