Putty and Primer Issues

[rocketrider]

Ok, I have been awya from this hobby too long.

I used the white Squadron White Putty on my Trade Federation Tank, sanded, puttied, etc, then primered it (testors primer in the can). I still have mold lines where I could have sworn they were gone. grrr

I am wet sanding this stuff after it dries overnight. Should I be dry sanding it?, does the water do something to it that im nor seeing, and is the green putty better?....

Any help or tips here on how you go about doing this the right way would be great.

thanks again

Glen
Moline, IL

[rossjr]

Personally, I would never use the green stuff again, given the choice...

Wet sanding should be fine but you need to make sure it is throughly dry before priming or painting.

I also like to use the Tamiya basic putty...

[Less Than Super Ostrich]

I got a tube of Mori Mori putty from HLJ one time. Awesome stuff. Will never go back to Squadron. Some are big fans of two part epoxy like Milliput. Two part epoxy never gets hard enough for me, IMHO.

[MarkW]

Squadron putty, white or green, seems to have a lot of shrinkage issues. I second the use of Tamiya putty--much more stable. For quick seam fixes, I use superglue mixed with regular (NOT cornstarch) talcum powder. Here's my thesis on the subject...

http://mysite.verizon.net/modelwerks/tips/SGT.html

As for sanding, wet sanding is almost always the way to go. The water helps keep the sanded material from clogging the teeth of the sandpaper, which extends the life and makes the sanding go faster.

In general, you gotta be careful with primers. Since many are lacquer based, they have aggressive solvents in them which can attack stuff like putty or even plain glued joints. I always take my time putting primer on--light coats, plenty of dry time between coats, etc.

[cougar184]

use automotive glazes. stuff does not shrink and you can sand it in about 5 min so no waying to dry. it also does not shrink back!!

[ignatz]

Maybe the seam is loose. Try applying gap-filing super glue, like Zap-A-gap. Then sand that down when it hardens. The glue will secure the join and serve as a very good filler too.

[Sluis Van Shipyards]

I'm having problems with that red Testors stuff. I fill sand, then yell "Damn!" Fill, sand, "Damn!" Then repeat. So I'm thinking my SW contest entry won't get finished in time. I'm gonna try some of the stuff suggested too.

[star-art]

Read this thread for some excellent advice on the best putties to use for modeling:

http://www.rpf.invisionzone.com/index.p ... opic=84294

[onezero]

You "still have mold lines" - what do you mean by that? Do you mean you still see the join lines between parts you've glued, or you still see the lines between where the molds were pressed together and the molten plastic injected into the molds squeezed out a bit?

If it's the latter - dude, putty ain't the answer. Sanding down the mold seam is the answer.

I'm guessing you meant the former, though.

Squadron's white and Green are not all that different than Bondo' spot putty, or 3M's Blue Acryl, or any of the other automotive spot putties. They all are a filler suspended in a solvent, in a toothpaste-like consistency. Squadron's products seem (in my experience -YMMV) to shrink more than Bondo or 3M .... perhaps more solvent? I dunno. I find that the the tube of Bondo spot putty I get at Wal-Mart for a buck and a half works better than Testors or Squadron, and lasts a lot longer as well.

For a plastic model, you don't need some fancy automotive 2-part epoxy applied while chanting paens to the self-annointed Modeling Godâ„¢. Don't get me wrong, if you want to go that route, it'll work .... but that's overkill.

I've built a ton of plastic models, most of them NOTbeing state-of-the -art, precision engineered marvels like Bandai's Gundams. I have display cases full of limited run, low-pressure injected marvels from obscure French and Czech companies - so I think my experience relevant to your particular problem.

The first trick to eliminating seams is not to have them. By that I mean use a 'hot' glue like TENAX and clamp the parts, so that a small ridge of melted plastic is pushed up where the parts are joined. Hit that with a sanding stick and you're golden.

That doesn't help fix where you're at now though - and it doesn't work as well when the edges of the parts don't line up well - like, say, a HiPM kit. Or the Polar Lights Enterprise (especially the warp nacelle pylons). In this situation, I use superglue to fill in the bulk of the gap. This has the added advantage of keeping the seam from popping/cracking open again as you work on it later. Then I come back with the Bondo spot putty (red stuff, probably the exact same chemical as in the Testor's Red Stuff tube, but half the price).

Now, all solvent-based putties shrink - a little (Bondo) or a lot (Squadron White). And most are less hard (abrade more when sanding) than the plastic on either side of the gap. I find that if I sand the putty down smooth, I still have a shallow 'ditch' along the joint, because the putty has sanded away more than the plastic. I cover this with Mr Surfacer 500 (a very thick lacquer-based paint), let cure, then wet sand again. Superglue, the runny stuff, works as well here also - hit it with an accelerator and sand immediately though. When superglue cures fully, it's harder than the surrounding plastic and you end up with the opposite problem - a raised bump along the joint - if you wait too long to get sanding.

Sometimes it takes several applications of putty, Surfacer, superglue, etc to get the seam to disappear. OK, for me - most times it takes several applications of putty, Surfacer, superglue, etc to get the seam to disappear. You learn patience this way.

[seam-filler]

Some are big fans of two part epoxy like Milliput. Two part epoxy never gets hard enough for me, IMHO.

Then you're not getting the mix right. Milliput, properly mixed, will set rock hard. I have successfully sculpted and filled with it for over 20 years. I have sanded, drilled and milled the results too.

It is easy to get it wrong, though. But to get best results here are my pointers:-

1. Make sure the 2 parts are as exactly the same size as you can. The easiest way to do this is to only mix small quantities at a time. It is easier to judge if you pull off a small bit of the harder (darker) part and roll it into a ball the size of a pea. Then do the same for the softer part. Because the second bit is softer it's easier to get it to match the other for size. Don't try mixing up too much at once - it's too difficult to get the quantities matched.

2. Knead together the two parts between your fingers for at least one minute. Longer is better. It helps if your hands are warm. It helps if your hands are clean before you mix - grease can reduce milliput's adhesive properties and it might fall off the model. It's also easier to mix 2 small balls than it is larger quantities. It also cuts down on waste - which is a good thing because milliput is not cheap.

3. Apply using fingers or whatever tools you want. Don't apply too much - it will dry harder than either plastic or resin and although you can sand it, you may end up taking too much of the model when you do. Make sure the model itself is clean and grease-free.

4. To make application easier to work you can use warm water to soften it as you work. This will also give a smother finish. Use even more water and milliput will trun into a sort of mud. This is really useful for filling fine seams & gaps or where sanding afterwards will be difficult.

5. Let it cure. Although it hardens to the point of being unworkable in an hour or so, it will not harden for about 4 or five hours. This time is extended is you worked it with water. Thicker sections take longer to cure. Milliput is a real pain if you try to sand or drill it when it's half cured.

6. As I found to my cost, it does hava a shelf-life. The harder component eventually gets too hard to work, so you can't mix it properly. This seems to be particularly true of the Superfine White and Silver-Grey. I use the Standard Grey/Green all the time as it is cheaper, doesn't have as short a shelf-life and there appears to be little difference in then end result anyway (apart from colour).

Why do I use milliput? It is hard. It will stick to almost anything. It doesn't shrink. It can be sanded, drilled, milled, etc. It doesn't attack plastic or resin and doesn't stink. It can be used to produce thick sections or fill ruddy great holes and gaps. It takes paint extremely well.

It's not the only filler/putty I use, and it's not the easiest to use, but I think it's the best for most applications.

[rocketrider]

I said mold lines, I meant seams

Glen

[rocketrider]

I said mold lines, I meant seams.

and thanks to all for al the input

Glen

[Less Than Super Ostrich]

Some are big fans of two part epoxy like Milliput. Two part epoxy never gets hard enough for me, IMHO.

Then you're not getting the mix right. Milliput, properly mixed, will set rock hard. I have successfully sculpted and filled with it for over 20 years. I have sanded, drilled and milled the results too.

Perhaps I wasn't clear enough... Milliput can be brittle. It works well for certain seams, but not for places that would receive alot of weight and/or pressure, IMHO. Particularly for scultping... Kneadatite works better for me. You said it was good for milling... i'm very surprised by that. But we are all entitled to our opinions.

[seam-filler]

Perhaps I wasn't clear enough... Milliput can be brittle. It works well for certain seams, but not for places that would receive alot of weight and/or pressure, IMHO. Particularly for scultping... Kneadatite works better for me. You said it was good for milling... i'm very surprised by that. But we are all entitled to our opinions.

I hear what you're saying, but I still think it's a mixing issue. I was using Milliput in the industrial evironment of the shipbuilding industry long before it was commercially available. We were even 'trained' in its use by a guy from the company that makes it. Mixed properly, milliput has extremely good mechanical & load bearing properties. However, too much of the soft component, the result will be soft and crumbly and easily damaged and too much of the stiffer component, the result will be brittle and less likely to stick to anything.

I do have my bad days and get the mix wrong, so one does have to take care when mixing. Some would see this as a disadvantage - but it doesn't particularly bother me.

I don't know the product Kneadette (probably not available in the UK), but other products I have tried suffer from either having to be heat-cured and/or shrinkage. The big disadvantage with milliput, especially when sculpting, is its cost (probably more so in the States).

All this, though, is horses for courses and everyone has their favourites. I got my high-horse a bit because I have seen the criticism of milliput too often on this site and peoples' complaints are not down to the product, but rather, the incorrect use of it.

I use a variety of fillers for different things (even acrylic wood filler for vinyl because of its flexibility).

[Less Than Super Ostrich]

Sounds like you have much more experience with this than I do. I'll defer to your wisdom, seam-filler. Perhaps I should experiment on the mixture more. Do you use water when mixing your Milliput?

[seam-filler]

No, I don't use water whilst actually mixing, but warm fingers really help. It wouldn't hurt to moisten your fingers, though. I do often use water as I actually apply it to the model - warm water helps here. A little water will make it a bit stickier and pliable. A lot more water will actually make a sort of sludge or mud which works into seams really well.

The critical thing is the 1 to 1 mix. Keep the prortions small because it's easier to judge that 2 small lumps are the same size than 2 big lumps. Also, as I said before, mix for at least a minute - if not more. Knead & squeeze it between your fingers (great stress relief too!). It wants to be the consistency of soft dough and a uniform colour - any streaks and it isn't mixed yet. This is one reason why I prefer the standard grey/green as it's easy to spot streaks.

Milliput is easier to work when it is warm and moist - but a lot of heat will cure it faster. A hair drier on sculpted milliput will surface-harden it within minutes.

Good luck.

[Lsutehall]

Hey Seam-filler, since you seem to be Mr. Milliput, could you give me some advice please? I'm having a hard time finding a good way of sanding the stuff. It seems to react very well to heat, and turns into a flat blob on my sandpaper/files, making them useless. What do you use to sand with?

[TER-OR]

Wetsand the epoxy putty or resin. It will keep your sandpaper cleaner and keep dust out of your lungs.

[seam-filler]

Lsutehall - Like Ter-or says, use your sanding sticks or wet&dry paper wet. Water doesn't affect cured milliput (the stuff will even set underwater!), so you can use as much water as you like.

Water not only keeps the dust down, but acts as a cooling/cutting/lubricating agent, much in the same way as machinists use "cutting fluid" on lathes, drills and milling machines.

If you're sanding a large area (say, if you're sculpting) add a little dishwasher rinse-aid to the water. This helps lubricate the grit and so make the wet&dry paper (or whatever) last longer and cut better.

[Lsutehall]

Thats great guys, cheers. I was just thinking about the nastyness of breathing in epoxy dust after reading the thread about resin. Is epoxy dust as bad?

Does anyone know where i can get hold of some good wet n dry sanding sticks in the UK?

[seam-filler]

Thats great guys, cheers. I was just thinking about the nastyness of breathing in epoxy dust after reading the thread about resin. Is epoxy dust as bad?

Does anyone know where i can get hold of some good wet n dry sanding sticks in the UK?

Breathing anything not made up of a mix of nitrogen and oxygen can be harmful. Even if the epoxy isn't carcenogenic (I would think so, but I don't know for sure), the fact that tiny lumps of it are building up in your lungs means that you are slowly suffocating yourself. This is where wet-sanding reduces the amount of dust in the atmosphere. I personally don't use a mask while sanding, unless I'm using a motor tool, merely because I keep my sanding wet.

But it doesn't end there! You have to clean up this 'sludge' and dispose of it safely - otherwise you're just making the dust a problem later.

Same goes for spray-paint overspray.