Paper Hardener

[MordecaiThrace]

Hey guys, my first real thread. I plan on building some paper tank models for use in Warhammer 40k, and I definitely want to use something to strengthen the cardstock. I am familiar with working on pepakura armor, but I have never done the fiberglassing or resin for those. I know Resin though would ruin details on a model that small. Do you guys know of any kind of spray hardener that would make the exterior of my model paintable as well as giving it some durability?

[lehcyfer]

Maybe something of this will help you.

If you get really good, you may have a new career. Dentists charge a fortune where I live, your future looks bright! (Personally, I could not be paid enough to look into people's mouths all day long).

[Vortex_4200]

Originally Posted by Zathros

If you get really good, you may have a new career. Dentists charge a fortune where I live, your future looks bright! (Personally, I could not be paid enough to look into people's mouths all day long).

That is the tooth the whole tooth and nothing but the tooth!!

[MordecaiThrace]

Haha, yeah, that might work. I read with pepakura armor that if you didn't want to go crazy and use fiberglass, you could use this weird stuff that you spray on that hardens paper. That might be good for a project like mine.

[lehcyfer]

The other way is using wood hardener like this. It is not a spray, but it easily penetrates entire volume of paper, dries fast so you can apply it again until the paper is full and doesn't absorb it anymore.

I wonder if there's an aerosol Viagra!?! I don't know if it would work but making paper models is intimate, however, the sight of scissors or an ex-actlo knife could cause the paper to fail immediately.

[kirkhere]

On another forum someone mentioned they coated paper models with a few coats of urethane, which hardens well.

I've not tried it yet, but have it in mind for my next project.

[Vortex_4200]

A russian site I saw a guy using drywall mesh tape and epoxy for hardning, urethane sounds intresting, where did you see that at?

[PilatusPC21]

VERY late to this game and contributing answers to your question, Mr. Mordecai Thrace. I hope this is still relevant to you and others.
I've been building paper/cardboard-based models for a long time and have kept a sharp eye out and experimented with many combinations of substances to achieve rigid, durable finishes.
My primary drive has been for building large scale R/C models and sci-fi spaceships; I've just never been satisfied with desk-top, paper fold & tab display pieces.

Honey brown polyurethane glue is one of the easiest and hardest coatings you can use, although it does discolour and is UV sensitive unless painted. It is also kinda nauseating for smell & prolonged skin exposure, but it is 1-part use instead of 2-part mix, like epoxy resins--you are not racing against set-up/cure times with it.
Only caution is pre-treat your hands with LOTS of lotion(helps prevent any sticking and speeds clean up!), wear gloves, pre-warm your working amount so it runs/thins easier(just like honey when cold!) and keep it AWAY from moisture & water. This will cause premature foaming & curing and can lead to a bubbly, messy end product quickly(will also dry out an entire bottle of new PU glue in short order!!). Some people pour a tablespoon of mineral spirits/thinner into a Gorilla Glue bottle after opening; as it creates a hydrophobic protective layer against atmospheric moisture w/out harming the glue.
Otherwise it has excellent absorbance & stiffening properties for fibrous papers.
Now, slightly more 'toxic', but quicker drying/curing, easy to make, store and VERY sandable, moldable, correctable(for mistakes...) is M.E.K. solvent with styrene plastic or ABS scraps dissolved into it. Compatible with practically all modeling adhesives, it is basically the same formula as plastic model cement--the MEK evaporates very quickly leaving the styrene behind as a paintable/brushable, runny goo. This becomes solid when the solvent has all gone--as fast as acetone left to air!--and results in plastic scale model density/rigidity plastic.
At whatever thickness/thiness, colour, texture you desire. If you took a paper-card model Sherman tank and brushed the liquified styrene onto it in uniform, thin coats you would end up with basically a scale, styrene plastic model kit, just as if you bought it from the hobby store & built it!
You can add acrylic or enamel paint to this mix and your styrene will accept whatever colour you desire. The only problem with applying successive layers to a paper or card model is that the first layer will soften and potentially 'lift-up' if too much solvent is reapplied. Like uncured layers of paint, it will soften and slough off, ruining whatever look or work you achieved prior.
It is often easier to apply your desired density or thickness in 2 or 3 carefull coatings, then sandpaper or file off excess later. Or...carefully massage in extra MEK solvent to melt away excess.
Excellent for indoor scale models and things to be kept from summer heat and sunlight(just as sensitive as plastic kit models...). ABS plastic can be 'alloyed' in to improve temperature sensitivity if you want outdoor, summer play time and particularly a good coat of enamel paint upon the finished work.
The advantages over epoxy are generally ease of preparation & cheapness, storage and cure/set-up time as you are not carefully mixing 2 proportions. Disadvantages are less durability, more heat sensitivity but ultimately sufficient for most hobby uses.
Did I say its CHEAP?!? Old model kit sprue trees, old broken models, toys, packaging and particularly bulk styrofoam waste!!!! Peanuts, computer/stereo packing, coolers--bloody cheap and abundant! Just drop it in the M.E.K. and it dissolves like ice cubes in hot water.
NOW...BAD nEWS=Very toxic for skin & lung contact and A LOT of VAPORS! Worse than epoxy exposure on skin & nasal membranes, BUT not as violently stinging OR debilitating as Cyanoacrylic/Super Glue vapor mercifully! Just use it in open air, open garage or adjacent to a window w/an oscillating fan blowing or drawing fumes outside. Normal eye, skin and mask precautions as with epoxy or other solvents.
I have been hoping to work with this for a long time and have now started this very week. I am creating new, thin-shell fuselages for 3-channel, cheapy IR coax helicopters--very abundant and in improved varieties this holiday season!
I took a particularly cheap one apart to make repairs, marred the supplied fuselage and decided I could improve on it. I'm making paper-card scale fuselage patterns on paper and painting them with the liquified styrene. It helps to smooth out any stepped angles of paper joints, allows model kit detail to be etched & scribed or further laminated and above adds much strength for little weight gain. if I make it too heavy, more solvent helps slough it off judiciously.
Sorry I cannot post pics at the moment but use your imagination! God, resources & time allowing, I hope to apply this in composite techniques to R/C plane models of 5-7ft wingspan in the season ahead. Anythings possible!

[a380]

i use insta cure thin ca glue. works really well. turns paper/card into something like styrene. figured out one trick. soak the part from the reverse side of your visible surface. helps avoid the glossy hard residue that sometime occur. downside is the price, about $5.00 for a 1 ounce bottle. the fumes are a problem when using larger quantities. i wear a respirator. started experimenting with minwax wood hardner. so far not hardning as much as ca. haven't tried sanding yet. pint bottle about $10. health warning on bottle. definetely use respirator. really curious about the dental products. will research

[PilatusPC21]

One important thing to add--I got caught up in rambling over the "Do's 'n Don't's" of handling M.E.K. and failed to address M. Thrace's central requirement for paper stiffening: proof against washing out/ruining printed colour detail.

M.E.K. will likely RUIN printed & colour detail as a spreading, bleeding solvent. So pre-treatment of the card pieces in PVA/water-thinned Elmer's glue and allowed to dry is my best recommendation to lock in printed details.
Then brush on the the MEK-thinned styrene solution, careful to do this in a spot with ambient warmth & dryness to encourage faster evaporation and deter bleed.

Hopefully I'll have completed test pieces to post by week's end.

[Patron_zero]

Maybe I'm old school-caveman primitive but depending on the model I've had fair success with a wash of thinned white glue mixed with finely shredded/chopped paper fibers.

Such applied on the 'interior' face of said individual pieces.

[sakrison]

A respirator mask is no guard against the fumes from CA or resins. Work in a well-ventilated area or outdoors. I installed a small bathroom-type exhaust fan over my workbench with a vent to the outdoors. I boxed it in with scrap wood and a cover made of 1" insulating foam, to keep the Great White North from invading our rumpus room in the colder months.

I don't use the fan much since I gave up plastic-bashing.

Originally Posted by sakrison

A respirator mask is no guard against the fumes from CA or resins. Work in a well-ventilated area or outdoors. I installed a small bathroom-type exhaust fan over my workbench with a vent to the outdoors. I boxed it in with scrap wood and a cover made of 1" insulating foam, to keep the Great White North from invading our rumpus room in the colder months.

I don't use the fan much since I gave up plastic-bashing.

There are a lot of master modelers using CA, the stuff is cyanide based. I got really sick off of a part of chopped Kevlar I was machining. The ball end mill ran a little hot and we were trying a new design. These were the blade tips for the CH53-E. They had a pure nickel cap bonded onto the chopped Kevlar end cap. at 412 degrees Fahrenheit, the fumes were adsorbed into the Lusol, and I absorbed it through my skin, highly diluted, so it went through my skin. Threw up like crazy. The stuff works great, but I stay away from it, except for the gap filling stuff which has to be some of the handiest stuff around! From forming parts using play dough as molds, and making or building up for repairs. I just fixed a key on my sons Laptop, (brand New, Aargh!) and it worked so well, I haven't had to order a new key or keyboard (which is actually only 4 dollars more than the single key!). I don't like using it but I won't use any of the above mentioned solvents anymore. I have found with ZIP DRY and the other UHU glues, these models stay together just fine.

Of course, I am not building these 1:1 scales that Ekuth does, where a Tig welder and some sheet metal might be worth considering!!