Dye for Sanding Gelcoat

[advgaia]

I'll be doing some gelcoat repair on my boat and would like to find a cheaper alternative to the Dry DyeCoat that TotalBoat sells @ 72$ per small container.

Is there an alternative that's affordable for a DIY small project?

I'm not looking for pigment dye to change the color of gelcoat. I'm looking for the dye to use while sanding between different grits.

[SailingHarmonie]

How about Prussian blue machinist layout dye? Not sure it’s actually cheaper, but it’s more common.

And there are a lot more choose for dry guide coat than total boat. Shop around

[Uncle Bob]

Mabee guide coat from an automotive paint supplier?

[John_Trusty]

I saw an experienced fiberglass artist check his sanding with an ordinary pencil. He scribbled lightly over the small repair and sanded it off, just like others use the spray telltale. I asked, and he said it was the old school method he learned and just took a little longer to apply.

[more]

Originally Posted by advgaia

I'll be doing some gelcoat repair on my boat and would like to find a cheaper alternative to the Dry DyeCoat that TotalBoat sells @ 72$ per small container.

Is there an alternative that's affordable for a DIY small project?

I'm not looking for pigment dye to change the color of gelcoat. I'm looking for the dye to use while sanding between different grits.

Exactly what is wrong with the gelcoat that it needs refinishing?
Are you repairing chipped, scraped or cracked gelcoat?
Or, simply restoring lost gloss

[hlev00]

Originally Posted by SailingHarmonie

How about Prussian blue machinist layout dye? Not sure it’s actually cheaper, but it’s more common.

And there are a lot more choose for dry guide coat than total boat. Shop around

Prussian blue has a grit. It is used for lapping surfaces.

[s/v Jedi]

I have used pencil scribbles and I’ve seen others use rattle-can paint. Rustoleum sells guide coat spray cans for $12

[JBP]

I have heard that cheap spray paint will work. You can clean it off afterword with solvent.

https://www.autobody101.com/forums/v...ic.php?t=20438

[rls8r]

I used Dykem Steel Blue layout fluid (similar to Prussian Blue as mentioned by SailingHarmonie - but no grit). It's miscible with alcohol, so I diluted it about 4:1 alcohol: Dykem. 4 ounces will cost about $12.50 and will last you the rest of your life. I've also used it for sanding primer paint before rolling & tipping.

[Bellinghamster]

Prussian blue doesn't have a grit, it's a very opaque ink in a non-drying oil, used to identify high (or low) spots of mating surfaces (precision machined, scraped or ground surfaces). You use a diamond or other grit paste to do the lapping, then check the result using Prussian Blue. Unsuitable stuff to use for fairing - There is no good reason to add oil to a surface you probably want to stick something to, plus it's messy and would gum up your sandpaper.

Dykem could work but seems like overkill for fairing (also can be messy as is very viscous - i.e drips/runs/wicks easily

I use a very light dusting of cheap contrasting color quick-drying rattle can spray paint or purpose-made guide coat spray paint. I like the idea of the pencil (graphite) method for small areas or gross leveling, but for finding pinholes and small low spots on a large surface, guidecoat is the way to go.

Now I'm thinking more about Dykem - it might be handy to mix up and spray apply? I'll have to give it a try!

[SailingHarmonie]

Originally Posted by hlev00

Prussian blue has a grit. It is used for lapping surfaces.

No, it does not.

Prussian Blue is the name for a specific blue dye. Machinists use it to coat surfaces so they can scratch guide makes into it. Kind of old school now with cad/cam systems so maybe you haven’t ever actually used it. Because clearly you are confusing it with something else.

[SailingHarmonie]

Originally Posted by Bellinghamster

Prussian blue doesn't have a grit, it's a very opaque ink in a non-drying oil, used to identify high (or low) spots of mating surfaces (precision machined, scraped or ground surfaces). You use a diamond or other grit paste to do the lapping, then check the result

……

Now I'm thinking more about Dykem - it might be handy to mix up and spray apply? I'll have to give it a try!

Actually, Prussian blue is the dye used in Dykam. It is just a different formulation of the dye to the oil based dye used to check progress of lapping. That fluid does NOT have grit in it, but it is used when lapping so I guess that is what has people confused.

But bad on me for not mentioning a specific product, since Prussian blue has many different uses. What I was trying to point the op to is layout fluid, which most certainly does dry, and in my shop was always called “Prussian blue.”

[Tsuru]

Originally Posted by JBP

I have heard that cheap spray paint will work. You can clean it off afterword with solvent.

https://www.autobody101.com/forums/v...ic.php?t=20438

+1. Use flat black spray paint. I use Prussian Blue regularly and don’t believe it’s the right thing for this application. Highly solvent, dark blue dye, with no abrasive. It’s used for metal lay out and lapping (for lapping abrasive is added).

[advgaia]

Thanks to all of you for your answers and suggestions. I had thought of the pencil method, and will try that first. The areas are small(er) and don't believe it should pose a problem in the final result. The cheap spray paint could be an alternative.

Thanks again.

[hlev00]

Be sure to do a test using spray paint. It could be a real mess if it doesn't work out. Otherwise go for an actual guide coat such as from Rustoleum.
https://www.rustoleum.com/product-ca...de-coat-primer