Sandblasting Preparation

[R Dub]

First time poster, seems to be an awesome community.

We have been providing sandblast redwood signage for 40 years.
With all the changes in products and some clients wanting water based
finishes we are not achieving the smooth process we have had for many years.
The first 30 years:
-We typically cleaned the freshly sanded redwood blank well
with a tack rag of mineral spirits.
-Apply two coats of a Marine spar varnish and two coats of 1shot with plenty
of dry time in between.
-Apply the cut stencil and protect the edges
-After the blast apply two or three Cabot's oil stain to the blast areas
while the stencil is still on.
-Peel the stencil after the last coat,
-Minor touch on the raised or finish colors-leaf
-Dry and done.

In recent years all these products have changed formulas or are not available.
It seems that the 1 shot is still a good product.
The (primer) spar marine varnish has been replaced by spar eurathane-not so
good
The cabot's oil stain is changing and tougher to find in our area.
Pre finishing with water base products does not seem to be a solution and much
more time consuming to finishing after blasting.

Does anyone have any pointers on products they use that hold up to the blast as well as the outdoors.

Thanks!
​

 

[James Burke]

What material are you using for stencil? Are you having stencil adhesion issues with the new finishes you're using?


JB

 

[James Burke]

You mentioned smoothness...are you having raised grain issues with the aqueous based sealers? If so, use a spray mist bottle and wet the wood, dry adequately then sand.


JB

 

[R Dub]

We use 3M stencil. I guess the main issues are:

The bond between the poly and 1 shot.

And any water based products that are good for the pre-finishing process.

What material are you using for stencil? Are you having stencil adhesion issues with the new finishes you're using?


JB

 

[J Hill Designs]

I still do it the same way as you list

I use man-o-war spar varnish (2 coats thin to soak, 2 coats full) then 2 coats 1-shot. blast, paint background (we rarely have natural background; usually solid-color stain, peel, touchup

 

[tbullo]

I use Sikkens Cetol marine on borders if I want a natural look there. Haven't tried it as a backround. It comes in a light and dark. Then coat with cetol gloss.

 

[3Dsigns]

Belt sand your redwood blank with about 100 grit
Tack rag real good, blow off with air
Thin with some "Signlife 1st Step" primer with a little toluene,
Spray on a moderately thin coat. let dry overnight
Sand down the raised grain with 220 grit paper and tack rag it
Coat with 2 or three coats acrylic latex

If you want "glass smooth" "see your reflection" smooth
Thin some Sherwin Williams DTM 1 pint/gallon
Strain it through some pantyhose into an HVLP gun
Spray overlapping strokes starting front to back of the blank
with gun slightly angled toward he back of blank
smooth as a baby's behind....... https://www.nglantz.com/2236248/Product/Glantz_Preferred_Supplier_

I don't sandblast anymore because of heallth reasons but when I do prepare one, for my local monument company to blast for me, that' the way I do it. But definetly wear a respirator, because Signlife/and toluene are NASTY stuff. I think you can feel your brain cells frying.
This is a step-by-step I did of HDU back when I was blasting. I just CNC now.... http://www.letterville.com/steps/wayne/index.htm
http://www.webbsignworks.com/index_htm_files/485.jpg

Oh yes, I forgot. I use Anchor #153 computer-cut stencil