Learn how to get perfect masking lines, also several different masking materials explained.
In the last masking article, I covered the very basic masking supplies needed for powder coating and also the reasons you would need to mask. In this article, I will show you some not so common ways to mask off parts when powder coating and also show you how to get nice, clean looking masking lines.
One extra step for nice, crisp, clean masking lines:
When you mask off a part with high-temperature tape, the tape can stay on the part the entire time the part is cured in the oven. However, you will find that after the part is done and you try to remove the tape, that the powder around the edge of the tape can flake off leaving a very jagged, messy line. This jagged line doesn't look good or professional at all. I will explain my method to avoid these messy masking lines.
You will need to work fast but carefully to do this. You don't want the part to cool down to much. If the part is too cool, the powder can flake off. If the part is too hot, the powder will be stringy and stick to the tape as you pull it. The stringy powder can land on previously masked area, ruining the clean line. Right around 180-200 degrees F is the sweet spot for pulling the tape. Keep your infrared thermometer handy and check the temperature as you unmask your part. On large, extensively masked parts, the part can cool too much leaving you with flaky lines as you unmask. If you find the part has cooled too much, you can re-heat the part using a heat gun or a torch at a distance. Once you have heated the area back up to 200 degrees, you can start removing the tape again. Alternatively, you can transfer the part back into the oven again to re-heat it if you do not have a heat gun or torch. I personally have a Milwaukee heat gun sitting close by when unmasking. It has 150-1000 degree F temperature range. Once a part cools down too much below 160, I heat up the area with the heat gun in one hand, and my infrared temp gun in the other hand.
After all of your masking is removed from the part, you then put it back in the oven and continue as normal: set the temperature as specified by your powder's instructions, wait until the part reaches that temperature, and then start your timer. Once the part is done and comes out of the oven, you will see beautiful, crisp, clean masking lines. This method also opens the door to many different types of masking materials that cannot withstand 400 degrees like the high-temp powder coating tape can.
Alternatives to High-Temp Powder Coating Tape
3M Blue & Green Painters Tape
3M Painters tape is much easier to work with than the high-temperature powder coating tape as it is able to conform around bends. The 3M painters tapes I have used and had success with is the standard blue painters tape and the green Automotive Performance Masking Tape. The 1" wide rolls seem to be the most versatile. The blue painters tape can withstand about 200 degrees in the oven, can conform around mild bends, and isn't as sticky as the green tape. When you are masking a part with gloves on, tape that is not so sticky is actually a blessing.
The green painters tape comes off easy even after reaching 250 degrees, can conform around more complex bends than the blue, and has a much stronger adhesive. The green tape is actually somewhat stretchable so it is very good for complex parts. The only issue with it is when you are masking a part wearing gloves. The green tape likes to stick to the gloves more so than the part so there is a little bit of a battle there. This type of tape cuts easily with scissors, a razor blade, or a scalpel. However, when using a scalpel, it does not leave as crisp of a line as the high-temp tape.
When using either of these tapes, it is very important not to let it get too hot in the oven. If you forget about it and leave it on the part for a full cure(~400 for 10 minutes), it will no longer be easy to remove. If you have ever tried removing the regular beige colored masking tape after it has been stuck to something for a couple of years, you will have a pretty good idea of what this painters tape is like if you leave it in the oven too long. The adhesive burns and the tape turns hard. It will peel off the part in pieces leaving a huge mess. Just remember not to use this tape for a full cure. If you use this tape, make sure to follow the instructions above.
Aluminum foil is a great way to mask large areas that would otherwise take many rows of tape. Aluminum foil is fine in the oven at any temperature involved in powder coating. Aluminum foil obviously has no adhesive properties so it will need to be supplemented with tape. Apply a piece of tape where you want your masking line to be. Lay out your aluminum foil to cover the area you want to mask off, but you want the edge of the aluminum foil to hang over your piece of tape a little. Then apply another piece of tape on top of your original tape, sandwiching the aluminum foil in-between. Aluminum foil is a great time-saver and much cheaper than tape for the amount of area it covers.
Glad Press' n Seal
Glad Press'n seal is a great, although unusual, way to mask large areas when powder coating. For those of you that have never used it, it is basically a saran wrap that can actually stick to other things other than itself. You can see one application here:
I was able to mask off the interior of this oil pan in less than a minute using the Glad Press'n Seal. To use it in this type of application, just follow these steps:
- Lay the Press'n Seal piece on your bench with the sticky side facing up.
- Lay the part to be masked upside down on top of it and press it down.
- Turn part over and really press down the Press'n Seal to make sure it is stuck to the part.
- Turn part upside down again.
- Take a scalpel or razor blade and trim the excess off around the outside edge of the part.
It is great for parts that have large flat areas like this oil pan, it also works well on valve covers, heads, engine blocks, etc. The downside is that it the Glad Press'n Seal cannot handle any oven temperatures without shriveling up. It must be removed before the part enters the oven. I do this by very carefully peeling up one area with a scalpel and slowly pulling it up. Make sure that no powder fell off of the Press'n Seal onto the area that was masked, then put the part in the oven and cure as usual.
Powder Removal: Wiping with a damp finger
The last form of masking I will talk about in this article is not really masking at all. There are some situations where you will get better results by spraying the entire part with powder, even the area you wanted to mask, and then removing the powder from this area before you put the part in the oven. This is best done on raised areas, such as the raised letters on a intake manifold, valve cover or brake caliper. You can remove the powder using many different methods. Below I will explain one of the methods.
You can use a damp finger to actually wipe powder from a raised surface. Keeping your finger slightly wet helps the powder to stick to your finger and not just brush off onto another area of your part. I keep a cup of water and a rag at my side. I dip my finger in the water and wipe off the excess on the rag, just leaving my finger slightly damp. Then carefully I start to wipe off the powder. The trick to this method is to only wipe a very small section at a time so the powder doesn't build up. I wipe about 1/2" with my finger, before I clean my finger with the rag, re-dampen my finger, and repeat. When you wipe, do so to collect the powder on your finger and not brush it off onto your part. It takes some time, and you must be extremely careful to only wipe what you are meaning to wipe. One little bump into a good area of powder, means starting all over again. It is best for your part to be sitting on a solid surface if possible.
|Uncured powder wiped from mating surface using damp q-tips.|
So now that you know a couple new ways to mask off your parts before powder coating, I am going to wrap up the article with one more piece of advice.
When you mask off a part using high-temp tape, foil, etc., it is only good for one coat of powder. If you want to spray 3 coats of powder, you should mask the part 3 times. Trying to re-use the same masking for more than one coat always ends up looking terrible. When I was new to coating, it took me so long to mask things, I thought the idea of doing it all over again for another coat was ridiculous. I didn't unmask my part and just used the tape that was already on there for the 2nd coat. The edges came out terrible. The lines were flaky and jagged, the powder actually bulged up on the edges and I ended up having to completely redo the part. By trying to save time, I spent much longer in the end, so just take my advice and re-mask for every additional coat.
Thanks for reading and if you enjoyed what you read or have any questions, feel free to leave a comment. Stay tuned for the next article. See more masking techniques in the previous Masking article.