Sandblast Slate?

[SqueeGee]

I have done the occasional sandblasted sign over the years and have a friend who would like one on slate for the end of his driveway. He's already got the slate (14" x 20" x 1" thick) and I have another buddy who has a sandblasting cabinet that it will fit in so I wouldn't need to drag out all the big stuff. I've also got a leftover roll of sandblast stencil, so I won't need to buy anything - I think.

My question is, since I've never blasted slate before - Is there anything special that I need to look out for? How deep should I blast it? Will it look ok without filling the blasted area with paint or should I plan on painting it?

Thanks for any suggestions!

 

[SqueeGee]

Lunchtime bump. Anyone?

 

[J Hill Designs]

I would imagine contrast would be poor if not stained or painted...

 

[iSign]

not sure if this is even relevant, but I had a laser engraving sample done on a piece of tile, that looked like slate.
It looked pretty cool to me.

It wasn't done to any depth you could even notice though.

On your slate project, I'd ask the friend if he had a scrap. Is it a dusty porous surface that will be difficult for the mask to stick to? Maybe a sealer of some kind would slightly change the color & sheen before you blast, while also giving a better surface for mask to adhere to... and then the blasted portion will have a better contrast without painting...

...OR, with better adhesion on the mask, you could then paint the blasted area through the mask with less care required on your edges. Having a scrap of extra slate would allow you to test these theories...

 

[Pat Whatley]

I used to blast that stuff all the time using sandblast mask, play sand and a gravity feed spot blaster (looks like a paint ball gun) that I bought at Harbor Freight. Slate is soft, it blasts really easily. (I'll also admit I only wore my painting mask so I'm probably dying of silicosis right now)

The main thing to watch for is flaking. Check your piece really well and make sure there aren't loose layers exposed on the surface. Make sure when you peel the mask off you pull it toward the letters whenever possible to avid putting a lot of strain on the blasted edges.

You're gonna have to do something to the lettering for it to be visible after you blast it. I spray painted most of mine before removing the mask, gold leafing it is incredibly easy and looks awesome for years or once I clear coated the blasted letters. The clear made them slightly darker and much more visible (except when the slate was wet, then the letters disappeared).

If you want to practice just run to Home Depot and grab a couple of slate floor tiles. They're cheap, they're plentiful, and you'll get a feel for what you're dealing with.

 

[CanuckSigns]

we laser engrave slate all the time, the laser can't get any depth really, but it does hold paint surprisingly well

 

[signmeup]

I've blasted marble and it was pretty easy. Slate must be similar density. I used Hartco 425(?) mask. The letters would look better painted in my opinion. Pretty easy since you will already have a mask in place. I used a blasting cabinet with a siphon gun. Pretty wimpy! I never tried with my pressure pot but it would have to be faster. If you don't want to do a whole lot of this it's not much problem. If you want to compete with someone who has pro gear you're in for a tough haul.

 

[SqueeGee]

If you don't want to do a whole lot of this it's not much problem. If you want to compete with someone who has pro gear you're in for a tough haul.

Definitely don't want to compete. I would typically refer something like this to someone else but...

Thanks for all of the suggestions.

Any particular paint to use? Would spray bombing it hold up sufficiently well?

 

[signmeup]

Even if you do out source it, it's nice to have done the process yourself at least once. Gives you some idea of what to ask for/expect. I'd use Krylon fusion as a first test.

 

[James Burke]

I use Lithichrome for my monument work. It dries within seconds and lasts for years.

Watch your depth, and make sure the areas that contain "islands" (A, O, e, and so on) of letters are not in any areas that are prone to flaking.

The new Hartco 900 series is really good stencil material if you have to go deeper than 1/8". Be sure NOT to get HT (High Tack) or you'll pull the slate apart upon removal.

We do tons of engraved brick using the Hartco 310 with 80 grit aluminum oxide and it holds up extremely well. We also use it to do river stone and granite and have even used it on slate.

JB