# "Filler Primer" and "Sandable Filler Primer"

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#### jqavins

##### Joseph Avins
TRF Supporter
I recently went looking online for Ruso filler primer, and found two products. One is called "Sandable Filler Primer" and the other is called "Filler Primer".

"What's the difference?" says I to myself. "Obviously you can sand either one" So I asked Rustoleum tech support. Here is their answer.

The 2-in-1 Filler & Sandable Primer is an 12 oz spray can and is more durable than the 11 oz Filler Primer.​

In case anybody else was wondering.

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TRF Supporter
Thank you!

Interesting.

#### kuririn

##### BARGeezer
TRF Supporter
Ah, that really clears things up.
Now I know which one to get.

#### jqavins

##### Joseph Avins
TRF Supporter
Yeah, I doubt the difference in durability matters to most of us; when it does we'd probably be using Bondo or epoxy. I think the one to get is whichever one is on the shelf.

#### Nytrunner

##### Pop lugs, not drugs
Does one clog the paper less.

##### Lonewolf.... No Club
TRF Supporter
Does one clog the paper less.
Yes. The Rusto 2X can be sanded, but it clogs the paper more than the Filler Sandable. I used the 2X on my F-79 nose cone, then sanded it, then added filler, then sanded it, then primered it with Filler Sandable.

Also, the Filler Sandable seems to enable heavier coats and is truly a flat finish.

The 2X seems more like semi-gloss paint than primer, IMO

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#### neil_w

##### Hunkered down and slowly going crazy
TRF Supporter
Yes. The Rusto 2X can be sanded, but it clogs the paper more than the Filler Sandable I used the 2X on my F-79 nse cone, then sanded it, then added filler, then sanded it, then primered it with Filler Sandable.

Also, the Filler Sandable seems to enable heavier coats and is truly a flat finish. The 2X seems more like semi-gloss paint than primer, IMO
We're actually talking not about the 2X here. Rather, on the Home Depot site, they show both "Filler/Primer" *and* something called "Sandable Filler/Primer" which they only sell in 6-packs.

Rustoleum's succinct answer is, shall we say, not particularly illuminating.

Absent any further info, I'll assume they're generally equivalent for our purposes. If someone wants to spring for a 6-pack and do some testing for us, then by all means.

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#### Philip Tiberius D.

##### Old Fashioned 2.5oz Rye/H2O 8 drops Orange Bitters
Lowe’s is closest to my house and Rustoleum Filler/Primer, DupliColor Automotive Filler and Rustoleum 2in1 Filler & Sandable Primer. DupliColor and 2in1work great - DupliColor might have more suspended particles and fill quicker. Neither clog sandpaper badly as long as I give them time to dry. The Filler/Primer is a distant 2nd or 3rd.

#### RocketTree

##### Active Member
Rust-oleum 2x primer takes around 1-2 weeks to cure, which is crazy. Before that time, you get nothing but plugged sandpaper. It works great on plastic, so I keep using it

Have also been using Duplicolor Sandable FILLER primer and it is excellent on body tubes. You can sand it with 320 after a day or two and ready to paint. I also use it to fill the tube spirals with use of masking tape and a small paint brush.

#### Back_at_it

##### Well-Known Member
I used to have good luck with Rustoleum primers but the last few cans I have bought have given me nothing but issues with cracking and separation. I've tried the sandable, 2X etc and i'm not having any luck. I've even had a couple of issues where it won't stick and can easily be wiped off with nothing more than a little pressure from your thumb. I've followed the same process for years, Sand the tubes with 800, wipe with rubbing alcohol then prime. For plastics I sand with 400, wash with a green scotch brite and dish soap, alcohol wipe then do light coats of primer letting each dry about 30 mins between coats.

I've always ensured that both the paint and the rocket were warm to the touch. This time of year I leave everything outside for a while before priming.

After the last can separated to the point where I had to sand the entire rocket back down to bare tube, I tossed the Rustoleum out and will never look back. I’ve switched to SEM high build for my last couple of builds and couldn’t be happier. It costs more but you don't use as much and my results have been a lot better.

#### Scott_650

##### Well-Known Member
I’ve used both high build and sandable, they are different but the difference isn’t that big. High build fills in a bit better (obviously) and the sandable is less likely to clog sandpaper. As others have said letting any primer dry completely can reduce clogging up your sandpaper. High build seems to fill in wood grain a bit better.

##### Lonewolf.... No Club
TRF Supporter
I've followed the same process for years, Sand the tubes with 800, wipe with rubbing alcohol then prime.
Why would you rub with alcohol? I've never heard of that?

How long are you waiting between the alcohol rub and the actual application of the primer?

Using a solvent before priming seems problematic.

#### Scott_650

##### Well-Known Member
Why would you rub with alcohol? I've never heard of that?

How long are you waiting between the alcohol rub and the actual application of the primer?

Using a solvent before priming seems problematic.
I typically use Dollar Store window cleaner - sprayed onto the paper towel, not directly on the parts - before I primer/paint. I let it dry for as long as it takes to shake the paint, usually 3-4 minutes. Never tried alcohol but as fast as it evaporates it probably wouldn’t interact with the paint. Interesting.

#### jqavins

##### Joseph Avins
TRF Supporter
For me, the rapid evaporation is the main thing. A damp cloth removes dust and the rubbing alcohol I keep on hand is only 9% water so it dries very fast. And I think alcohol may be less damaging to cardboard tubes than water if some does soak in, but it's mainly the fast drying.

#### Marc_G

##### Well-Known Member
I use the Rusto Automotive Filler Primer bought in the auto section at Walmart, not in the paint section. Works great and sands well without too much clogging.

#### Back_at_it

##### Well-Known Member
Why would you rub with alcohol? I've never heard of that?

How long are you waiting between the alcohol rub and the actual application of the primer?

Using a solvent before priming seems problematic.
The Alcohol wipe is the last step in prep to get any oils or contaminate off the surface. How long I wait after the wipe down depends on outside temp. If it's cool outside i will use a hair dryer to warm the rocket and the paint. If it is warm I'll sit everything out in the sun for 10-15 mins to let it warm up. Alcohol evaporates almost instantly and I'm not soaking the tubes. The towel is only ligthly damp.

I've been doing this same process on Rockets, RC Cars, full size cars and just about everything else I have ever painted with a spray can for 30+ years without too many issues. It's only been the last few cans that I've purchased in the past year that have given me issues. In all hoenesty I'm glad I ran into these issues as it pushed me to find an alternative that I like better.

#### Event Horizon

##### Well-Known Member
Automotive wax and degreaser actually works pretty good if you're concerned about oils from your skin getting on the rocket. Frankly I wash my hands with Dawn dishsoap often while working on rockets, it prevents oils from getting on the rocket. Using a cloth or paper towel lightly wet with the degreaser and wipe down. Let it dry for a bit and then use a tack cloth to remove any dust or particles.

#### DES

##### Member
Because everything is required to be as complicated as possible while increasing opportunity for sales, Rustoleum has multiple primer offerings.

I have found the best of the bunch to be the Rustoleum "Ultimate Finish" Automotive Primer. This is a lacquer base, fast drying, medium build primer. Dries fast, sands easily, does not clog the sand paper. Adheres well (except to polyethylene nose cones), has a nice tooth to it. If the paper has a build up on it, you can clean the paper with by scrubbing a bit with a paper towel. Most of the other Rustoleum primers and spray paints are acrylic alkyds, a hybrid oil base paint, which are slower drying and a bit gummy until they cure.

To quote Dilbert - We cannot compete on quality, and we cannot compete on price. That leaves fraud. Which we will call marketing...

##### Lonewolf.... No Club
TRF Supporter
Because everything is required to be as complicated as possible while increasing opportunity for sales, Rustoleum has multiple primer offerings.

I have found the best of the bunch to be the Rustoleum "Ultimate Finish" Automotive Primer. This is a lacquer base, fast drying, medium build primer. Dries fast, sands easily, does not clog the sand paper. Adheres well (except to polyethylene nose cones), has a nice tooth to it. If the paper has a build up on it, you can clean the paper with by scrubbing a bit with a paper towel. Most of the other Rustoleum primers and spray paints are acrylic alkyds, a hybrid oil base paint, which are slower drying and a bit gummy until they cure.

To quote Dilbert - We cannot compete on quality, and we cannot compete on price. That leaves fraud. Which we will call marketing...
Note to those who don't know. Just don't spray that lacquer over a previously applied enamel or acrylic.

Enamel over Lacquer ... Good
Lacquer over Acrylic or Enamel .... bad

Lacquer over Acrylic or Enamel.... Paint Herpes

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#### neil_w

##### Hunkered down and slowly going crazy
TRF Supporter
Note to those who don't know. Just don't spray that lacquer over a previously applied enamel or acrylic.

Laquer over enamel... Good
Acrylic or Enamel over lacquer.... Good

Enamel over Lacquer... Paint Herpes
Lacquer over Acrylic or Enamel.... Paint Herpes
Did you type that correctly? Looks like you contradicted yourself re: lacquer over enamel and enamel over lacquer.

My understanding was that lacquer-based primer was pretty safe to put anything on top of.

I'm most curious about how much build you get from this primer. I normally apply one pretty heavy coat as my filler/primer step. Will this stuff do a good job as a filler, or will I be looking at multiple coats? Likewise, how much build does this stuff have vs., say, the regular Rusto 2x primer?

#### Scott_650

##### Well-Known Member
I'm most curious about how much build you get from this primer. I normally apply one pretty heavy coat as my filler/primer step. Will this stuff do a good job as a filler, or will I be looking at multiple coats? Likewise, how much build does this stuff have vs., say, the regular Rusto 2x primer?
Roughly the same price. High build has a higher “solids” content and does a good job of filling scratches and does, somewhat, fill BT spirals AFTER normal filling/sanding of (in my case with diluted Elmer’s CWF) spirals. It won’t fill spirals all by itself of course, but I typically only use one medium-heavy coat of filler/primer, then sand, then either final coat or white undercoat depending on the rocket. With regular primer it’s coat, sand, coat, sand so it saves me a step. Not a huge difference but anything that cuts down on sanding is worth it to me ;-)

#### neil_w

##### Hunkered down and slowly going crazy
TRF Supporter
Roughly the same price. High build has a higher “solids” content and does a good job of filling scratches and does, somewhat, fill BT spirals AFTER normal filling/sanding of (in my case with diluted Elmer’s CWF) spirals. It won’t fill spirals all by itself of course, but I typically only use one medium-heavy coat of filler/primer, then sand, then either final coat or white undercoat depending on the rocket. With regular primer it’s coat, sand, coat, sand so it saves me a step. Not a huge difference but anything that cuts down on sanding is worth it to me ;-)
I wasn't clear in my post, but I was specifically inquiring about the Automotive primer that @DES mentioned in his post above. Trying to get an idea if it will still function as a high-build primer the way I am accustomed to, which is exactly as you describe above. DES said it's "medium build", which leaves me uncertain.

#### Scott_650

##### Well-Known Member
I wasn't clear in my post, but I was specifically inquiring about the Automotive primer that @DES mentioned in his post above. Trying to get an idea if it will still function as a high-build primer the way I am accustomed to, which is exactly as you describe above. DES said it's "medium build", which leaves me uncertain.
I’ve used this as well - same $4-5 price range. It seemed to have a lower solids content than high build though it did sand very nicely (as always, after it thoroughly dries - any paint I’ve used loads up sandpaper more if it’s not completely dry - if I ever get my shop cleaned up and organized properly I’m making a drying booth and a paint booth!). Bottom line is I grab whichever filler/primer is on the shelf for the lowest price- the key factor being the “filler” in the name, any filler/primer is going to fill imperfections better than straight primer. At$4-5 a can you can try a couple types and find out what works best with your building style/techniques without busting the budget.

#### neil_w

##### Hunkered down and slowly going crazy
TRF Supporter
the key factor being the “filler” in the name, any filler/primer is going to fill imperfections better than straight primer.
The Automotive primer DES mentioned does not have the word "filler" on the can, as far as I can tell.

You're right of course that experimentation is the normal way to resolve such questions. My spraying opportunities are generally extremely limited, though, so experimentation in this area is very tough for me.

#### MALBAR 70

##### More Rockets Than Room
I usually use Rusto 2in1 Sandable Filler/Primer some times just the regular Rusto Automotive Primer.

I've used both of these with varied success. The Zinsser is an acrylic primer and the Kilz is an oil based primer (it's important to note that you must be very careful to make sure your top coats are compatible). Both, although not a filler primer, are very "fluffy" and fill nicely and sand quite well, without too much paper clogging.

#### DES

##### Member
I’ve used this as well - same $4-5 price range. It seemed to have a lower solids content than high build though it did sand very nicely (as always, after it thoroughly dries - any paint I’ve used loads up sandpaper more if it’s not completely dry - if I ever get my shop cleaned up and organized properly I’m making a drying booth and a paint booth!). Bottom line is I grab whichever filler/primer is on the shelf for the lowest price- the key factor being the “filler” in the name, any filler/primer is going to fill imperfections better than straight primer. At$4-5 a can you can try a couple types and find out what works best with your building style/techniques without busting the budget.
The Rustoleum automotive primer will typically take 2 to 3 coats to fill the spirals on Estes paper tubes. The fill will actually be faster if you sand between coats, as that way you are not only filling the valleys, you are knocking down the high spots (and preventing the high spots from getting higher). The first coat should be moderately heavy, let dry for a full day or two, then sand with 180-220 grit dry, until about 50% has been removed, and the tube is peaking through the primer like leopard spots. Then apply a second coat, and depending on the alignment of the planets, good chance it will be smooth and level.

The automotive primer will fill the grain on balsa as well after 2 - 4 coats, but if you want glassy smooth on balsa, some sort of wood filler before primer works a bit better. I use a thin film of epoxy to fill balsa.

I don't care for the spray can "fillers". They are soft, slow to cure, and build the whole surface, rather than just fill the depressions. In my opinion, they provide a soft layer under the relatively harder surface coats. A thin primer provides a better finish.

##### Lonewolf.... No Club
TRF Supporter
Did you type that correctly? Looks like you contradicted yourself re: lacquer over enamel and enamel over lacquer.

My understanding was that lacquer-based primer was pretty safe to put anything on top of.

I'm most curious about how much build you get from this primer. I normally apply one pretty heavy coat as my filler/primer step. Will this stuff do a good job as a filler, or will I be looking at multiple coats? Likewise, how much build does this stuff have vs., say, the regular Rusto 2x primer?
Fixed it... Thanks Neil

Lacquer over enamel (or Acrylic) is dangerous territory.... more HERE

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