A weird thing happened today while carving a sign

[jim shula]

It's a 6"x60" sign with a flowing script font. Most of the letters are connected. I primed the extira and painted it with two coats of aura, my usual paint. I masked the whole thing using the 15" wide yellow Gerber sign mask, then started carving on the shopbot. Instead of cutting the masking cleanly, it left real ragged masking edges and completely tore it off on some letters. It's like the masking wasn't sticking real well.

When I saw this happening I stopped the toolpath, tore off the masking up to where the toolpath ended and tried again. Same result. My first thought was a dull vbit. I ran out and bought a brand new one and tried again with the same results.

Now I have two possible causes in mind. Maybe the surface was stippled from the roller. Usually I'll buff between coats with a sanding sponge or scotchbrite pad. On this sign I didn't. Could this slightly rougher surface cause the masking to lift off too easily?

The other possible cause is that on the same work table the painted sign blank was sitting on last night, I sprayed some wd-40 on a microwave oven I was cleaning up. Could a little bit of overspray have settled on the sign and caused adhesion issues with the masking? Maybe this is a stretch, but the sign was about 3' away in the path of the spray.

Also, if I put new masking on a sign that has already been carved, can I expect the vbit to cut the masking cleanly?

[RossMosh]

It's probably a combination of the two. As someone who's had a few failures, it's typically a combination of 2-3 things that causes a problem like this. My guess is the change in the paint method has more to do with things than anything else. Are you using the exact same paint you've used in the past? Did you go to gloss instead of semi or flat? These could also be contributing factors. Did you let the paint dry all the way? Could also contribute. Personally, I don't like rolling my signs. I like applying with a HVLP gun. If you can, look into this as it will help get you a much smoother, flatter finish which should help with the masking. The only real trick is to get a gun with the biggest tip you can find. 2.5mm is he biggest I could get.

I'm going to be perfectly honest, I've been in this position before and I'd just start the process over unless you're pretty experienced with a brush. It's unlikely that you'll be able to put the piece down again and re-carve it with any success. The next option is going back and putting the mask on and hand cutting around the letters which I find to be a complete waste of time and doesn't look all that great after all said and done. The only way to get something that looks good is to hand paint, but that takes a certain amount of talent which I don't have. So I typically take it on the chin and start over.

[jim shula]

Yep, I already made another sign blank. Hand painting all those letters with no mask is the very last resort. I'd be better off carving it, then laying on the mask and trying to trim with an exacto knife. I still have the old one for testing, and found that if I rub the paint down with denatured alcohol, the mask really sticks well. But rubbing it down removes the nice uniform sheen of the low lustre paint finish. Damned if I do and damned if I don't. I tried a sample piece of mask on the new sign and it pulled right off. I tried to heat the mask with a hair dryer and roll it down with a laminate roller. That seems to help a little. It's got the same rolled finish with the same paint I've used on hundreds of signs in the past, and it's pretty smooth. Maybe I'll try spraying another coat on it.

[RossMosh]

Based on what you're describing, it's a paint issue. I can tell you based on Joe Crumley's recommendation I've been using Nova Color paint and 100% Acrylic DTM paint and it works great for masking.

Out of curiosity, how small of letters are you carving?

[chunkstyle]

I just recently noticed a similar issue when cutting thru paint mask on a surface that had paint applied with a roller as you mentioned Jim. Luckily for me it didn't matter for the fonts I noticed getting ragged edges. It was subsequent pocketing/ V carving that was going to need to be painted and I did what you did using a laminate roller to 'burnish' down the mask and make it stick better to the latex paint I was using. It is a local brand that I've been using for a while now and never had an issue with the Avery paint mask I have been using along with it. If you look at the attached picture you'll see what experienced
http://www.talkshopbot.com/forum/attachment.php?attachmentid=27598&stc=1

It's hard to see but The upper case "C" and "G" have tear out along the edge. Less visible tear outs were also present thru out. Sorry for the poor picture quality but this was all I had that spoke to your problem. That's the first time I've had it whereas I hadn't seen it when I was applying paint with a sprayer, laying out real flat vs. rolling it on.
Also noticed a lot of air was trapped when I rolled it with laminate roller.
Peeled off like it was half as tacky too.

[jim shula]

The letters are about 4" high so it's not like there is little room between them. It's the very end of a roll of Gerber I've had for three or four years. Is there a shelf life on that stuff? I just used it on a 1'x8' carved sign painted with Ben Moore blue danube a few weeks ago and it was fine. The paint I'm using on the current sign is Ben Moore jet black Aura.

[fredtoo]

I can generally tell if the mask is likely to lift when I apply the mask. If I think it will lift I take the extra time to lightly score the profile of all the letters with a sharp 60 degree v-bit and sometimes remove the mask inside the letters so it doesn't wrap around the bit when routing.

[jim shula]

Good idea Fred. The Gerber Ultra mask is almost two years old, and they said the adhesive can go stale. They guarantee it for a year. A new roll will be here tomorrow so I'll give that a try.

[chiloquinruss]

I have never tried this and I have a mask job coming up so I will report back - my idea is to put the mask down and then shoot a very thin clear coat on the mask, let dry and then cut. Might just harden the edges enough to get a good edge. My reason for trying this is I also have an OLD mask roll! :D Like I said I haven't tried this method yet!

In the past I have sprayed the CUT mask before coloring the letters, this makes any bleed CLEAR, let the clear dry, then color coat, then let dry, then remove the mask. Very sharp crisp edges. Russ

[jim shula]

I tried something else this morning on the sign blank I'm using for experiments. I have some MasterClear for clear coating over Modern Masters metallic paints. I thought maybe if I sealed the paint with that, the mask would stick better. And it does stick much better, but I don't like the wet look of the clear coat over the satin paint.

[RossMosh]

Based on what I'm reading I think you should try to spray your signs and try another brand of paint. One of the issues with latex paints is they are constantly changing. Ben Moore Aura paint may have been brilliant to use 5 years ago but they could have changed the formula last summer and now it won't work as well. I've never used it so I can't comment on how good it works with masking now vs in the past. Also could be just a bad batch of paint. Might be worth buying another quart to see if it helps.

[bleeth]

If at this point if you just want to move forward you can "break down" the sheen with 4x steel wool and some oil or water or a quick run with some compound.

[jim shula]

The new roll of Gerber Ultra arrived today so I tried a few test pieces on the sign blank. It stuck marginally ok when I first stuck it on, but after rubbing it in hard and waiting a few hours the adhesion was much better. Maybe Saturday I'll get a chance to try carving it.

[jim shula]

Just a follow up. I masked the sign with the new roll of Gerber. Right after I put it on the adhesion was not much better than the old roll I had been using, but I left the sign in by the woodstove for a few days while I was off doing a boat show, and when I returned the mask had a good grip. I got it carved and painted the letters, then the mask came right off with no problems.

[chiloquinruss]

With all of the companies going 'GREEN' these days I think we will see more and more of these strange things happening. They change their components without knowing how 'we' might be using their products.

Glad you got it 'fixed'. I didn't know the mask has a shelf life so it was a learning experience on my end as well. Thanks for posting first the problem and then the cure. Russ