Basic problems with everything, esp. spray paint and glues, advice/opinions?

[AlanMintaka]

Hi Everyone,
I'm just getting into gluing and painting some of the structures I've been working on and have run into a dead end.  I won't go into my experiences with the so-called cyano "super glues" because that would take a book, and one of these topics at a time is more than enough.  Suffice it to say that the super glues are now in the trash and good riddance to them.

Spray paint problems: I'm working with foam core at the moment.  I found out the hard way that enamels do a number on this stuff, so after asking around I got some Tamiya spray acrylics and started practicing with that.

I started with flat gray primer.  I noticed some problems trying to get an even coat as this spray didn't spread around the same way the enamels did.  I practiced on test pieces for some time then applied the spray to the foam.  I was very careful but still could not get an even coat.  Since it was primer, I figured it wasn't so important.

It set up quickly but I waited a day to apply a top coat.  I selected "Gun Metal Gray" spray acrylic, Tamiya again, and began practicing. 

It was disaster.  No matter how hard I tried and how carefully I applied the paint, the result was grotesque rippling on primed foam.  Unprimed foam behaved the same way.  What could I be doing wrong here?  No matter what I do, it seems impossible to get an even coat of this stuff.  Even the areas where I applied a very light coat began to ripple as soon as I stopped spraying. 

Temperature wise I think I'm OK.  It's in the mid 60's F in the basement.  Following up on some other advice, I tried warming the paint can in mildly warm tap water.  I still got the ripples.

All the practice pieces are ruined.  The paint is rippled everywhere.  I figured the only thing I would dare do at this point is to forget the gun metal gray paint and put another coat of the gray primer on the finish piece.  There was no rippling on the piece from the first coat of primer, but sure enough the coat turned out to be uneven.  It was easy to see that much with the paint dried.

I practiced with the primer again on a few more throwaway pieces of foam until I was certain I had the hang of getting the primer on in an even coat.  Then I carefully painted the finish piece the same way.

I just went downstairs to check on the work.  Once again, the primer coat is uneven on all the pieces, practice and finish.

I'm at a loss.  I can't understand what I could be doing wrong here with these paints.  I know this stuff takes practice.  On the other hand all I'm trying to do is get a uniform coat of some kind of paint on foam core.  Enamel destroys the material and these acrylics either coat unevenly no matter how they're applied, or develop gross rippling patterns.

I should add that those "ripples" are in the paint, not the material.  Also, they don't seem to be lines of really think gobs of paint with thin paint in between.  There's no sign of running, drops, etc.  Viewed up close and/or touched with a finger, the coat is thin.  It seems like only the color that's rippling like that.

Does anyone have any ideas on this?  Sorry to make this so long.  I didn't know how else to report these problems without going into some detail about how I applied this paint.

Hope everyone's holidays are going well,
Big Al Mintaka

[lmackattack]

most paints that comes in a spray can will attack foam. There are a few that wont but I cant name any off the top of my head. In My experince you need to use a paint that is more water baised or laytex. most of these will not attack the foam. If this is scenery work brush painting the foam is all that is needed. I wont go into more details untill I find what your end goal is with the paint.

the thin CA glue is a PITA if you dont have the quick set spray to make it harden ASAP if this is what you had I know exactly what issues you had... LOL

Trent

[mabloodhound]

I'm not sure what you are doing.   You say you are spraying "foam core".   Is this the paper covered foam board?   What are you using it for?   Background scenery?
Or is the solid foam board?   Need more info to help you.

[CNE Runner]

Al, let me start off with one problem at a time. Let's clear the air about Foam Core and Foam Board (Gatorfoam). Foam Board (Gatorfoam) is a lightweight product, that comes in various colors and consists of a very dense plastic foam laminated with two layers of thin wood (usually luan). This is Foam Board:

Foam Board is an excellent product (a little pricey) for use in structures. Its wooden exterior can be used as is - or laminated with some type of overlay. Foam Board takes most paints readily as long as one remembers that the 'core' of the product is still plastic.

The product I have mentioned in several posts is Foam Core (I incorrectly typed it as 'foamcore'). Foam Core is also a lightweight product that comes in various colors. The major difference between Foam Board and Foam Core is that Foam Core consists of a dense plastic 'core' (very similar - if not the same as Foam Board) that is laminated with two layers of heavy paper. Given the porosity of the paper, and the vulnerability of the plastic core to solvent-based paints, one should always use acrylic paints. Here is a picture of Foam Core:

These two products have entirely different properties and must be used accordingly. I hope this helps with stage 1 or your question/thread. BTW: I use Foam Core exclusively - laminating it with printed paper laminates.

Ray

[CNE Runner]

OK, from your post you mention that you are using Foam Core...I will direct my advice to that product.

The major no-no with Foam Core is moisture...specifically too much of it. When you are priming the product (with an acrylic - water solvent - product) move the spray can across the piece very rapidly. It should take several extremely light coats to properly cover the material. All painting should be done in a warm room. Another suggestion is to use a blow dryer to speed the drying time (remember: too much moisture is a big problem - so you want to get rid of the liquid portion of the paint ASAP). I should tell you that the only part of a foam core panel I usually paint are the edges (I'm too cheap to purchase black or gray panels).

Use a low temperature hot glue gun (available from your local Hobby Lobby store) to fasten panels together. I will assume all door and window openings have already been cut. Test fit panels together with blue painters' masking tape beforehand.

I have mentioned that I laminate my foam core panels with paper laminates...thereby dispensing with painting step. Paper laminates can be view/purchased at Paper Creek Models at: http://www.papercreek.com/ and are relatively inexpensive [BTW there are other manufacturers]. I laminate a structure after it is assembled - making sure any joints (in the laminating paper) are in an area that is out of view.

Remember our discussion, in my last post, about too much moisture? Using white glues to excess will cause problems. Until you internalize the notion that less is sufficient, I would use glue sticks to adhere the laminates to the foam core. Doors and windows?..(you are going to love this...) - I use CA and sparingly (a tiny drop in each corner of a window or door).

Keep the faith. Modeling is a set of skills that takes a lifetime to learn. Trust me...we have all relegated projects to the 'circular file' at one time or another. Now get back in there and build some structures!

Ray

[CNE Runner]

I was going to modify my post above; but decided to write a new one instead. I had occasion to visit our [fairly] local Hobby Lobby yesterday - and found that some of the statements, I made in my previous post, were inaccurate. I would like to correct them:
1. The terms 'foam core' and 'foamboard' (or foam board...I have seen it spelled both ways) are interchangeable and are not related to the construction of the product. Gatorfoam is a patented product that takes foam core/board a step further in durability (it is still considered foamboard/core by the retailers).
2. I mentioned that Hobby Lobby only produced the white version of foam core. This isn't true as I was shown a display with three or four color selections (yes, black is included). Of note is the fact that no matter which color you decide fits your needs; they all have a white foam interior...which is rather strange in my opinion.
3  Hobby Lobby carries several sizes of foam core.

Not related, but noticed while I was in the store, is a neat cutting system that allows one to make straight cuts, 'V' grooves (useful in bending foam core - allowing the modeler to make an entire structure's walls with only one seam), 'free-style' cuts and circles. The products are marketed under the 'FoamWerks' [that isn't a misspelling] moniker and can be seen on the company's website at www.foamwerks.com if needed. WARNING WILL ROGERS!! The 'cutting heads' are expensive with the WC-6001 Straight Cutter selling for $29.99 and the W-3001 FoamWerks Channel Rail an additional $17.99 (I didn't price the other components). Doc Ray wants this 'toy'; but will wait for the 40% store coupon to save railroad funds (I take one coupon to a store and purchase an item, whist my wife takes another coupon and purchases a second item. If need be we do the samething at the second Hobby Lobby in town).

Check it out,
Ray

Sheesh...I just posted this and then thought of an other super buy. I picked up a low temperature hot glue gun, at Hobby Lobby, for $2.47 as well as a package of 50 mini low temperature craft sticks (or glue sticks) for the gun at an additional $2.47! Once in awhile we do score a good buy.

[AlanMintaka]

Hi Everyone,
Thanks for the great responses.  I can see by your questions where I didn't supply enough information, so here goes:

Project: 18" X 18" HO scale heliport deck.  No cutouts, a slight amount of custom trimming along the edges to fit the building frame.  Landing patterns and other markings will be added later using wet decals (I print my own on a color laserjet, no smearing).

The materials I've tried so far are:

• Fan-fold foam insulation sheets (Lowe's), laminated on one side with a very thin vapor barrier of clear plastic.  Too much surface rippling and other imperfections to be useful, spray enamel attacks it, spray acrylic can't be spread evenly (even the primer)
• Masonite, takes all kinds of paint, smooth surface great for the heliport, but the 18" X 18" sheet is too heavy for the structure.
• Foam core as described by CNE Runner: foam sandwiched between some kind of paper/carboard laminate.  In this case I got acid-free foam core at an art supply store where they use it for frame backing, so it costs big bucks to use it.  The surface can take spray acrylic or enamel.  Enamel that lands on the edges causes slight scoring but not enough to worry about.  As of tonight, spray enamel spreads much more evenly on this stuff than acrylic.   I may have solved my problem with spray acrylics right here via just not using them for this project.

I have yet to try brushing jarred arcylics on this material.  I will definitely experiment with that as I have enough practice pieces.  But if this type of foam core is what I'll be using in the future , I need to find a cheaper way to get  hold of it.

None of this solves my problems working with spray acrylics.  I'm far from being an expert at spray painting but with patience I can get decent coverage with the enamels.  The acrylics just won't spread evenly for some reason.  Maybe the option of using thinner with the jarred acrylics is what's missing here.

So I'm now shopping around for cheaper foam core.  I'm still too PO to talk about the glues, especially Gorilla CA and expoxy.

Anyway thanks once again for these replies, especially the photos in CNE Runner's response.

Have a good one,
Big Al Mintaka 

[AlanMintaka]

Hi Everyone,
Now that I seem to have found the right materials for the different structure elements I need, I've moved immediately on to a painting disaster.

I've been practicing with Krylon spray paints on high-impact polystyrene sheets.  The sheets are 18" X 24", .030" thick, opaque white.  If you've ever worked with Kenner's old Girder & Panel/Bridge and Turnpike sets, it's the same material used in the wall panels and roadways - only a little thicker.

Gray Krylon Primer went on very well, gave a nice smooth even coat, and didn't attack the plastic.  So far, so good.

I liked the color the way it was and decided to use the primer as is for the coloring.  However I found out through experimentation with this primer on other materials that it marks easily after it's dry.  So I decided to try one of the Krylon clear coats.  I waited a few days until the primer coat had cured (at least I thought it had).

Then I practiced a bit with Krylon clear satin on scrap pieces of styrene and wood.  Once I had the hang of laying on those materials, I started spraying the primed polystyrene sheet.

It came out horrible!  The nice uniform gray color of the primer is now splotchy.  The splotches didn't change after they first appeared.   Even though I continued until I had sprayed on an even coat they stayed the same.  What the...

I looked at the material from different angles to make sure I had an even coat of the clear.  The surface looked wet, smooth continuous, no dry spots.  I waited but there was no change in the splotches.  However I noticed after a while that I was starting to see the support shims underneath the sheet right through the plastic!  It's now semi-transluscent in some areas, splotchy in others, and solid gray in the remaining areas. 

What could this be?  The primer certainly didn't have any damaging effects on the plastic, but now the Krylon Clear Satin seems to have turned this thing into a wet oil painting on slowly melting plexiglass. 

Could this be

a. The primer not being really cured?  The clear coat could have semi-dissolved areas that weren't as cured as others, though why it would cure that way I can't figure.  Even if it weren't completely cured though, I still shouldn't be able to see through the sheet as the unpainted material was opaque white.

b. The clear coat does something to the polystyrene that the primer doesn't?   That makes no sense to me, but then neither does a blotchy clear coat that eats through primer and makes solid white polystyrene semi-transluscent.

c.  Something else, whatever that might be.  I have 4 kinds of Krylon paint here: the can of gray primer, 3 cans of "indoor/outdoor" colors, 3 cans of "Fusion for plastic" colors, and 3 cans of clear coat: flat, satin, and gloss.  Clear satin was the one I used on the primed polystyrene.  The other types of spray colors don't even figure into this.  Yet.

Has anyone else seen Krylon sprays do this to plastic before?

Thanks for your time,
Big Al Mintaka

[Jim Banner]

Most likely, the solvent from your clear coat penetrated the primer.  Primer is to help bond the finish coat to the base material.  It is not intended to seal the surface against all and sundry.  If you have every tried any auto body work, you likely have already found that the primer you put on bare metal has done almost nothing to keep it from rusting because it is not a sealer.  Hint - use plastic compatible paints, even if you have laid down a primer, then the solvent that penetrates the primer will not affect the plastic underneath.  For clear coating, there are water based acrylics that will do the job.

I assume you are buying your Krylon in consumer spray cans, not commercial drums, and that you are applying it with the spray cans, not an air brush or paint sprayer.  In this case, you might want to be careful where you buy your paints.  Ask the seller about the paints you are interested in - if he starts reading the label, it is time to move on to the next seller.  When you get to a paint store where they can go into detail about their products without having to read the labels, you have found your supplier.  Establish a relationship with him.  Buy ALL your paint from him.  If it costs a few dollars more than at the big box store, sill deal with him.  It will pay off in good advice and freedom from frustration.

Jim

[AlanMintaka]

Most likely, the solvent from your clear coat penetrated the primer.  Primer is to help bond the finish coat to the base material.  It is not intended to seal the surface against all and sundry.
...

I think I get the drift here.  Primer is a bonding agent for the finish coat, but doesn't necessarily protect the material from the finish coat paint.  In this case the Krylon clear satin was the finish coat, and it looked as though it had penetrated the primer and damaged the plastic - but see UPDATE below.

What bothers me about this is that both paints are Krylon indoor/outdoor, not the "Fusion for Plastic".  If the primer didn't hurt the plastic, why should the clear coat? 

However, there is an

UPDATE: now that the stuff has set overnight, the opacity of the primer coat has magically returned and it is now once again a solid color everywhere on the sheet.

Unfortunately the clear coat does look as though it dried in blotches in some areas.   To me it looked like the clear coat simply didn't cover those areas, so I added another coat just now.   I also added another support shim under the plastic sheet to make sure it was as flat as possible.

This coat filled in the previous blotches somewhat, but added more blotches of its own.  I think I know what's going on here.  Unless the material being painted is perfectly flat and level, Krylon clear coat flows away from the "high" areas and into the low areas.  This would be why the pattern of blotches looks different after I added the extra shim. 

Also, last night I painted some of my practice pieces with the Krylon clear to see what would happen.  These plastic squares were cut from the same high-impact polystyrene material.  They had been sprayed with a variety of paints - Krylon indoor/outdoor assorted colors, Krylon Fusion assorted colors, and 2 colors of Rustoleum.

One day later and I see that the Krylon clear coat has acted like paint remover on the Rustoleum "2x cover" Green.  However the Rustoleum flat black paint was undamaged.

And the blotches are showing up on some of these pieces too.  One of them was painted with the Krylon primer - no surprise there.  The flat black rustoleum shows blotches too.  But the Krylon Fusion Green doesn't.  There is a Krylon Fusion beige that might have blotches but it's hard to tell because the color is so light.

I'll be scanning and posting these as soon as they've set another day.  So far I can conclude the following:

Krylon primer doesn't bond Krylon Clear Satin.  The clear coat flows over the surface away from "high" areas and into low areas. 

Krylon Clear Satin does coat smoothy on Krylon Fusion For Plasic paint, but not Krylon indoor/outdoor paint.  It blotches on the latter too, flowing into low areas and leaving high areas uncoated.

This doesn't speak well for Krylon primer.  Since it is indoor/outdoor primer, it should bond indoor/outdoor paint.  It doesn't.  It does bond Krylon Fusion for Plastic.

As said, I'll try to post scans of the practice pieces tomorrow. You'll be able to see what I mean by these blotchy areas.  BTW the edges of those blotchy areas give off a rainbow hue of reflected light. 

...
I assume you are buying your Krylon in consumer spray cans, not commercial drums, and that you are applying it with the spray cans, not an air brush or paint sprayer.  In this case, you might want to be careful where you buy your paints. 
...

Yes, that's me.  I'm strictly a cut 'n' paste amateur.   I don't have fancy airbrush tools, compressors, or even a small spraying booth.  I spray in an unfinished basement.  I save my spraying jobs up until I have a good number of them.  I'm careful when I spray, at the right distance depending on the paint and results on practice pieces, in smooth motions, no starts and stops except between pieces when I'm "mixing" the rattle cans.  I move from one end of the assembled jobs to the other and then get out of the basement fast.  In warmer weather I spend more time down there because I can ventilate with fans.  Right now that's not an option.

I get the Krylon from Walmart or wherever else it's on sale.  I don't bother asking the assistants there about which is better for what task.  I do that online in forums, where I've been reading that Krylon arcylic lacquers (and the sythetic lacquers in spray cans) are safer for use on foam core than harda*** enamels like Rustoleum, which also dissolves skin and mucous membranes. 

The guys who know things work at Hobby Town in Nashua and are the only ones I've found so far who can talk about these paints.  Unfortunately they're very pricey.  The Tamiya Arylic jars are small for what I want to do with these large surfaces and would run up a pretty large expense tab.  They have a very limited supply of the spray synthetic lacquers too, in small cans and also high priced. 

I have some of the Tamiya in jars for small pieces.  I've been resisting using the sprays only because of cost, but now it looks as though the only way I can do what I want to do with plastic is to pay the big bucks.  I'm open to suggestion about how to buy larger quantities of Tamiya without breaking the bank.

You may be able to tell from my tone here that I'm a little discouraged for lack of progress, even with these practice pieces.  I have one of those HG Wells Martian War Machines here and I don't dare go anywhere near that until I figure out how to do this without wrecking the thing. 

One thing I've already decided about that War Machine though - I don't think I'll be using the Gold Leaf sheets like some of the hardcore modelers here and on the HobbyTalk forum!

More updates and scans to follow,
Big Al Mintaka

[AlanMintaka]

Most likely, the solvent from your clear coat penetrated the primer.

Hi Jim,
I have an update that corroborates your observation once and for all.

I tried the Krylon Clear "Flat" Indoor/Outdoor spray.  It worked fine!  I got a nice, even, flat, protective coat on Krylon Flat Primer.

Evidently it was something in the Clear "Satin" that was causing the problem.  I haven't tried Clear Gloss yet as I have no use for it at this time, but I'll be sure to practice with caution when I do.

Once again my status as a cut 'n' paste amateur keeps me from knowing the reasons for this property of Krylon Clear paints.  If I were working with Minwax Satin vs. Minwax Flat polyurethane in cans, I would say that the leavening agents in the satin caused the problem with blotchy coats on the primer.  However I don't know what ingredient makes Krylon Clear "Satin" as opposed to "Flat".

But whatever the difference is, it makes Krylon Clear "Satin" useless on Krylon Flat Primer: it sets up in large blotchy patches with rainbow-hued edges.  "Flat" gives such a nice even coat that even a nervous ex-drinker like myself can spray a smooth surface.

I now have a sheet of high-impact polyurethane, 0.03" thick, 18" X 18", with a nice gray surface covered in protective clear-coat.  The color is a very close match to the gray used in the roadway pieces in the new Bridge and Turnpike sets. 

I FINALLY got something to work with spray paints!  It cost a lot of money and a vague sick feeling for a day after I painted, probably because of fumes in the basement, but I got it done!

By the way, my success with this particular combination of material and paint is probably not a predictor of anything anyone else might do with the same stuff. 

Oh yeah, one more thing: the paint is very flexible when set up.  I can bow this sheet of plastic in and out from all sides and corners with no obvious signs of crazing, rippling, or wrinkling of the dry paint.

So there it is.  On to the next disaster, which will involve attempts to paint and/or decal landing patterns and walkways for a heliport surface.  I've read in this forum that gloss surfaces work best with decals.  I'm hoping to make it work with flat surfaces.

Humbly, and yet humiliatedly,
Big Al Mintaka