Oramask 831 topcoat spraypaint problems

I recently carved a squadron badge for a friend and it was my 1st time using the method of paint then lay down vinyl then carve then paint the carved area then peel the vinyl. I used Oracal 631, I was very pleased with the way that it carved. I used a quarter inch down cut bit an 8th inch down cut followed by a 60゚ V bit and it cut beautifully. I had spray painted white then carved it then I spray painted black on top of the vinyl and carved areas, I sprayed 3 Coats of Rest oleum 2X satin spray pain and let it sit for 24 hours. When I went to peel the vinyl the following day the adhesive did not stay on the vinyl it stayed on my work piece creating a ton of work using goo gone trying to remove the adhesive which didn’t really work, all it did was stain the white paint on the piece. I then had to go back and hand paint the entire thing.I have put spray paint in a solo cup before and it melted the cup so I’m not sure if there is a different kind of spray paint people are using when they use this method to finish their work or if I just need to be using latex or acrylic paint to finish after carving. Any assistance is greatly appreciated.

20191203_221227|375x500

1 Like

I don’t have any comment on the paint issue but that’s awesome! You got some great detail in there!!

1 Like

That looks great!

Maybe try using the expanded PVC sheets instead of paint to get the colors you are looking for? Gski191 and Dennis have made some pretty cool signs with the stuff like this and this. It might not work for the detail you are looking for, but if it works, it would eliminate the need for the masking and painting cycles in your work flow.

2 Likes

The adhesive for your material is specified as “semi-permanent”, not removable. I should guess that you want a different material, intended as a paint mask, which will have a low-tack adhesive.

The materials I have used for masking have low-tack adhesive specifically for the purpose and leave no residue on cured paint. On solvent paints (or water-based enamels, or two-part urethanes) that are not fully cured when the material is applied, removal without damaging the undercoat can be a challenge or impossible.

Paints set up in several different ways, but the common solvent-based spray paints undergo a curing process after the majority of the solvent has evaporated, which may take several days–longer in some cases. This is what the instructions are referring to when they talk about dry-to-touch, dry-to-handle, and full-cure times. Until FULLY cured, anything in contact may adhere to some extent, and the adhesive used on the vinyl film would be a good candidate for adhesion on any surface. The plasticisers in the vinyl may add to the issue, as might un-evaporated solvents from the paint. Depending on the paint, it may still be sensitive to solvents, and stick to some materials.

These paints may include a variety of organic solvents. Solo cups are polystyrene, which is tremendously soluble in a wide variety of the solvents used in paints (toluene, acetone, xylene, and so on).

I don’t know if a different paint type will improve the behaviour, but sufficient cure time won’t hurt, and a proper paint mask will certainly help (like Oramask or Greenstar, maybe. I think my mask shop uses Oramask810, but I would have to check… I don’t actually care as long as we can mount it under adverse conditions-- sometimes at sea-- and remove it after paint is applied).

You might try contacting a mask material supplier for advise.

3 Likes

@enl_public has good comments about the tape you used. As someone who designs tapes for a living, removable vs. non-removable is a very important distinction and changes a lot about the tape. “Masking tape” is for masking and is intended to be removed. Oracal is not a masking tape while Oramask is. Oracal 831 is an outdoor vinyl film with permanent adhesive while Oramask 813 is a masking film (hence the word “mask” in the name) that has a low-adesion pressure sensitive adhesive on it that will remove much better.

3 Likes

Yep, I was reading the OP and thought the same, it is not the right product for the job. I just bought some Duck Brand white (not transparent) removable adhesive shelf liner from Wallymart that has been recommended in another forum to try instead of the Oramask, as it is much cheaper and more readily available.

1 Like

@luc.onthego
I have a similar project I will be starting. Please let me know how it works and can you post a link for the duck brand liner if it works well. I am searching but not sure which product you are talking about. Also, is there a reason basic tan masking tape or green tape (3m brand) won’t work? I have noticed that Blue tape doesn’t mill nicely and can stick on the bit.

1 Like

I’ll give it a try very soon to see if it works well. Masking tape does not work well, just like painters tape, it lifts and gums-up the bit.

I had tried the transparent/translucent shelf liner (same brand) and it did not work at all, it lifted from the the workpiece.

I went to Wallymart in Canada to buy the shelf liner but I understand the same product is available in the USA. Here is a picture.

I observed this issue and ran some tests to check it. What I believe the issue stems from is the crepe-paper backing of masking tapes. It is fibrous and doesn’t cut as cleanly as the PVC backings of shelf liners or Oramask 813. Plastic is more apt to split and rip while the paper fibers can leave “fuzzies” and even is a few fibers aren’t cut, they can pull up the remaining tape.

Thus, I recommend using PVC or other plastic backed tapes as a mask for CNC work over crepe-paper masking tapes.

2 Likes

Here’s the link to it:

3 Likes

I mis spoke, this is the actual product i used. Thank you so much for all the help. This community is amazing!

I wonder if this could have been caused by the use of a satin paint. The adhesive may not release well from a surface that is not at least semi-gloss. I have just painted a piece of MDF with semi-gloss and will wait for it to dry before I try to apply the shelf liner for a test.

2 Likes

I had painted the MDF about a month ago. I laid the vinyl, carved and painted the topcoat a few days ago all within a 24 hr period. The vinyl from the outside of the profile cut, which did not get painted peeled off clean. Only the vinyl with spray paint on top had the issue. The adhesive seemed to become very gummy.

This sounds like solvents from the paint you used for the cover. I don’t know what the actual interaction would be, whether it was with the adhesive, the first paint layer, or both.

I would suggest doing some testing, but this makes it sound more like you might want to use a paint that is not organic solvent based, or change the mask material.

4 Likes

I think youre right on with that. I wonder what topcoat paint everyone is using with the oramask 831. Maybe ill change the name of the op to get some input

I ran into this exact same problem with oramask and rattle can paints when i first started using it. It happened once when I masked before letting the paint cure sufficiently, now I wait at least 48 hrs (72 hrs if humidity is high) before masking. That obviously is not your problem. The only other times I have had this happen is when I have had “skinny” slivers of masked detail like your sign that when applying the second color too heavily (either too heavy of a single coat or too many light coats in one session) ended up getting the same “gumming” issue. My base material was pine or poplar and my theory is that while drying the solvent gases were able to penetrate the end grain of the cuts and make their way in through edges of the “skinny” pieces of masking. Even if I am way off base with that theory, i now “re-press” the film over uncut portions after cutting to make sure the edges are still nicely adhered before the next round of painting. I also take painting nice and slowly (and use a proper primer or sealer) and that seems to compensate for whatever is actually causing the “gumming” issue.

Edit: I think @enl_public hit the nail on the head.

2 Likes

I had the same residue left over after one particular project. I had no issues using Oramask 813 before. This project was similar to yours. I sanded some birch ply with 220 and spray painted black. I let it dry for 4 to 5 hours then masked. I carved, sealed the carve with brushing lacquer, waited 30+ min to dry, and spray painted the carve. I waited for that to dry to the touch, and peeled. I ended up with several spots that had residue left behind. I typically do not paint my birch ply, but sand to 220 and seal with brushing lacquer before applying the mask. I never had any residue with just the lacquer.
BTW - I found that using a pink eraser works pretty well to get the adhesive off.
I’ve been using the Duck brand shelf liner for a few of the same type projects, and it leaves residue behind every time. It gets extremely gummy if using spraypaint to paint the carve, and is brittle in the areas with out paint over it. This is just my experience though. I have been leaving it on longer than I have wanted to (2-4 days). I need to do a project on a Saturday to see if the liner works ok if it is not left on too long.
I also bought a can of peel coat to play around with to use as a mask. I don’t really expect it to work, but I figured it would be an experiment worth trying.
No solutions here just observances.

Thanks for the great feedback! Ill be trying the same process again today up to the point of painting after carving. For topcoat i got some dutch boy premium paint and i plan to brush on instead of the spray paint. Carve, shellac, brush on top coat then peel vinyl is the plan.

1 Like