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Wrinkles/air bubbles developed in papier mache after applying gesso...

#1 2013-10-21 23:43:50

HLG
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Registered: 2013-10-21
Posts: 8

Wrinkles/air bubbles developed in papier mache after applying gesso...

Hi,

I'm having a bit of a problem with a papier mache mannequin I'm working on, and if you could offer some advice I'd really, really appreciate it, as I'm scared of ruining what I've done so far.

I bought it secondhand, so I'm not entirely sure what materials have been used, but from what I can see, it's made from a polystyrene armature, which has been covered in strips of newspaper (looks like 1, maybe 2 layers), followed by a layer of white paper strips. It's then been painted all over with some kind of white paint, and a design in black (maybe paint, maybe some kind of pen), followed by a layer of PVA (I think, as it was shiny).

I've done a bit of work on it, consisting of sanding the entire thing with very fine grade sandpaper, and I've repaired the nose and ears with PVA-based tissue paper pulp. I left those to dry for ages, and they became absolutely rock-hard, so I'm sure they're dry. I sanded those bits, and then I covered the entire thing with a coat of white acrylic gesso, let that dry for about 5 hours, then did a second coat.

It's the gesso that seems to have caused the problem, as I've noticed that a few small-ish air bubbles and wrinkles have formed under the surface of the strips (bits I haven't touched, other than sanding).

Is there any way I can repair/fix these air bubbles, and if so how? I'm scared that if I paint another layer of gesso onto it, that the bubbles and wrinkles will get worse because I'll simply be adding more water to it. I'd really appreciate any advice you could give me, as I need to figure out some way to get a nice smooth surface.

Many, many thanks,
HLG

Last edited by HLG (2013-10-22 01:10:51)

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#2 2013-10-23 01:14:22

CatPerson
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From: Washington State, U.S.A.
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Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

Did you apply rather thick layers of gesso?  Too much moisture (glue, gesso, paint, etc) can have that effect.  Paper swells and expands when it's wet, and shrinks when it dries.  If the paper gets too wet, it swells and then sometimes doesn't shrink back to the original "tightness".

Another issue (or combination of the two) may be that when the paper was applied, it wasn't burnished or pressed down firmly enough, and the contact wasn't tight.

Where the bubbles and wrinkles are, try this:  dampen the spot with a small artist-type paintbrush or a Q-tip.  Get it damp enough to be able to press down, but not sopping wet.  When it's damp, stick the bubble with a pin, then press the bubble down from the edges to where the pinhole is.  Press it firmly down so it makes good contact, maybe even burnish it down with the top of your fingernail or the back of a spoon.

You can also see this type of problem when the paper strips used have been CUT, as opposed to TORN.  For some reason, the cut edges tend to lift, whereas the fibers of the torn edges seem to grip better and stay down.  I don't know what the science of it is, but it certainly does happen.

Let me know if this works or not.  Maybe someone else will have other ideas, too.

Sue

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#3 2013-10-25 18:34:38

HLG
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Registered: 2013-10-21
Posts: 8

Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

Hi Sue,

Thanks so much for replying! :-)

I think the second layer of gesso I applied was a bit thicker than the first, so that might have done it. The gesso itself was a also lot thinner than I'd been expecting (I've read that some people put it on with a trowel!), I'd say maybe even slightly runnier than regular acrylic paint, but as I'd never used it before I just went with it. I think I'll be making the coats as thin as possible from now on, even if takes a little longer for me to build it up.

You may also be right about the papier mache not having been burnished properly. When I was sanding it, there were a few sharp bits where the edges of the strips hadn't quite been smoothed down. I've had a good look at it again, and the strips have definitely been torn rather than cut, which is something at least.

Thanks for the idea of puncturing the bubbles while they're damp, I'll definitely try that when I have some free time this weekend. I'll let you know how I get on.

Thanks again, I really appreciate it.
HLG

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#4 2013-10-26 04:47:40

CatPerson
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From: Washington State, U.S.A.
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Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

Commercial gesso IS thin.  I was surprised when I opened the bottle and poured some into a bowl.  However, multiple thin layers may be more effective for most things.  If, someday, you do need a thicker gesso, you can add chalk to it.  Chalk has many names, depending on the source:

Chalk, the stuff in sticks for writing on chalkboards.
Art supply shops call it whiting.
Pottery shops call it calcium carbonate.
Garden shops call it agricultural lime ("ag-lime").

The most expensive place is usually the art shops, about $1 per pound (bulk).

Experiment with thickness on something that's not important first.

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#5 2013-11-03 17:20:00

HLG
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Registered: 2013-10-21
Posts: 8

Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

Hi Sue,

That's good to know about adding chalk to it, to make it thicker. I may well do that on my next project. Thanks!

I've tried dampening and puncturing the bubbles like you suggested. It seems to have worked on a few of them, but several of the larger ones especially, are still there. Do you think making a small slit and brushing some PVA glue into the bubbles, then pressing them down, would help them to stay flat?

Thanks so much for all your help!
HLG

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#6 2013-11-03 22:04:14

CatPerson
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From: Washington State, U.S.A.
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Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

That is why I'm not overly fond of PVA glue, it's a plastic and can be difficult to remoisten and get it to do what you want it to do.

Try the slit, add the glue (but don't over-do it) and try to burnish it down.  You might have to press it down several times while it's damp, to get it to stick.

Isn't it wonderful to have all these 'learning experiences' as you go along?  Now you know how I learned most of this stuff.  A friend called it 'the Boo-Boo School of Learning', which seems appropriate.

If you haven't used it before, try methyl cellulose (MC) someday.  This is an adhesive made from highly processed wood fiber, so it's considered an organic adhesive along with wheat, potato and rice flour glues, but it's so refined that it doesn't seem attractive to insects and vermin like the 'food flour adhesives'. 

It is more air-permeable than the acrylic (plastic) glues, and is more quickly re-moistened, so a repair like you're doing would be easier.  It seems to dry faster, and you don't have the problem of only partly dried parts of thick layers, where they flex when they should be rigid, which you can have with PVA adhesives.

Some people mix the MC with PVA (white glue), but I've never seen the point.  To me, PVA has its uses, and MC has its uses, and I just decide which one is best for my current purpose.

I'm not sure where you are, but if you're in the U.S., a small container of Elmer's Art Paste is methyl cellulose, costing $3-4 for two dry ounces.  Mixed with COLD water, it will make up to four quarts.  It doesn't mold like the food flours, but I try to mix only small amounts, and vary the water content to my current need, usually the consistency of raw egg white. 

While it is water-soluble and can be washed off the 'harder' papers, it doesn't seem to absorb moisture from the air like the food flours, but it should be sealed with at least acrylic paint; if you're using a water-soluble colorant or finish, I would advise sealing it with shellac or a clear acrylic sealer.

Sue

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#7 2013-11-03 22:08:16

dopapier
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Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

I think that is a very good idea but only pva will really work in this instance.  Make sure the pva is not diluted, put just a smear inside the bubble; leave it for a short time to get really tacky before pressing down.  Once dry, you can use the surface treatments that you and Sue are sorting out.
DavidO


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#8 2013-11-03 23:08:51

CatPerson
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From: Washington State, U.S.A.
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Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

Oh, David, you're right!

My thoughts jumped from A (fixing the problem) to B (a different product) without the notation that B was NOT a fix for A.  It isn't! Sorry!

I was suggesting the methyl cellulose for other projects.

Thanks for catching that!

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#9 2013-11-10 05:12:26

HLG
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Registered: 2013-10-21
Posts: 8

Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

Wow, thanks both of you!

I hadn't heard of methyl cellulose before, but I've been reading about it and yeah, it sounds like exactly the sort of thing I'd want to use if I were starting from scratch. I'll probably get some for my next project. I'm in the UK, so it'll probably be a little more expensive over here, but it sounds worth it. :-)

I've done the slit/PVA repairs, and it seems to have worked. The bubbles are now gone, and the only evidence (for all but one) that they were ever there are some very small ridges where I cut through the paper. I think they'll sand off pretty easily though, so I'm really pleased.

The largest bubble is also now gone, but there's now a small, slightly bumpy crater there instead. Do you think that if I make some more papier mache pulp out of tissue paper and PVA (like I did for the nose and ears), that'll I'll be able to fill the crater with it, then sand it smooth? Or won't it stick to the gesso (even when sanded)?

And Sue, the Boo-Boo School of Learning sounds extremely appropriate!

Thanks so much for all your help, you've been fantastic!
HLG

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#10 2013-11-10 08:23:42

dopapier
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From: UK
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Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

That's good to hear it's going well.  Yes, you could fill a small area with pulp but it would be best to coat it first with a waterproof PVA, then apply a barely moist pulp, allowing to dry very thoroughly before doing anything else.
Starting from scratch will be much more interesting for you and, as you have seen, there are myriad examples in the galleries.
You won't find small packages of anything called carboxy methylated cellulose because it tends to be marketed in huge quantities.  In the UK only one firm that I know of sells it.  Pritt Papier Mache Paste comes in small packets as a fine powder.  It is actually CMC manufactured by a company in Finland, distributed in the UK.  Pritt repackage for the craft market.  It is available on the web and is supposed to be available in craft shops but I had difficulty finding it. 
It is used by specialist manuscript archivists.
If you can't find it, quite honestly, Polycell wallpaper adhesive works really well.  I mix it with about 25% PVA for both pulp and laminate.  Don't make up too much at a time and keep any spare in the fridge (clearly marked!!!)


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#11 2013-11-10 19:48:08

CatPerson
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From: Washington State, U.S.A.
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Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

HLG, while you can add PVA, I would suggest that you use it straight a few times to see what is what.  But keep in mind that PVA will slow drying, and it IS a plastic, so ask yourself if that is what you want for the particular project.

I have read on other PM forums that people will add all kinds of stuff to their adhesive, including dog food kibble!  But a good rule is not to add anything unless you know WHY you are adding it.  Don't get carried away increasing the number of ingredients just to do it.  Keep it simple.

David, it would interesting if someone contacted Polycell and asked what percentage of their adhesive is MC.  Inquiring minds want to know!  8-)

Sue

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#12 2013-11-15 09:10:23

mavigogun
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From: Istanbul
Registered: 2009-04-22
Posts: 106

Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

CatPerson wrote:

"HLG, while you can add PVA, I would suggest that you use it straight a few times to see what is what."

Sound advice that- becoming familiar with the haecceity of a material before adding other variables.

"But keep in mind that PVA will slow drying, and it IS a plastic, so ask yourself if that is what you want for the particular project."

Slow, compared how?   MC most definitely features qualities that lend themselves to expressive, impromptu work- such as crumple-building just-slathered paper into forms -but may prove too weak for large, unsupported work; it does absorb ambient and applied moisture (as does PVA, but at a differing rate), and thick application before drying can trap moisture- either of which can spell collapse.    As a shell over foam (think epic scaled Falles) which would be faster, MC or PVA?   If that same form were hollow- say a Mardi Gras mask?   Which would take longer to paint?

PVA is plastic- which is readily evident when rotary tooling: it melts, stretches.   This ain't usually a happy-making discovery.

"*snip* ...a good rule is not to add anything unless you know WHY you are adding it."

Sure, informed experimentation is wise- but submitting to circumstance and intuition is valuable, too.   Things work even if we don't understand why; lacking profound molecular chemistry insight, this is how much of pre-industrial technology developed- at a cost.   I reckon the best place to start for us is in the border lands- a cursory understanding of chemistry truisms, the historical use of ingredients, and how polymers are formed would be of service.   Compounds are oft much greater than their constituents.

Last edited by mavigogun (2013-11-15 09:17:24)

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#13 2013-11-15 09:49:57

dopapier
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From: UK
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Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

Good for you, Chris (mavigogun), bringing some philosophy into the arena.  I think one value of this community is that we individually contribute to the qualities you describe and, when combined, the thoughts, knowledge and experience add up to something worthwhile.


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#14 2013-11-15 19:30:23

CatPerson
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Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

'Slow' as using similar viscosities of MC and PVA under similar conditions.

Perhaps it is the humidity here, but with a thinnish eggwhite consistency mix of MC versus the usual half water/half PVA mix, there was no comparison.  The PVA was still very damp while the MC was almost brittle.  I don't usually subscribe to the "if a little is good, a lot more is better" with adhesives, myself.  (Chocolate, yes.)  Obviously, a thick, heavy layer of almost any adhesive is going to take longer to dry, and there is an excellent chance that the outside will dry faster, limiting the egress of moisture from deeper within the piece, especially if it is being formed on a moisture-impervious form (like a plastic ball or aluminum plate).

Also, since PVA is a plastic, there will always be some flex to it.  But if that is what you want, or it won't make any difference, it's fine.

No adhesive is perfect for all uses or projects.  That's why you need to explore the limitations of each one individually. 

'Compounds are oft much greater than their constituents.'

Chemically, yes, but a lot of money has been poured into knowledge and development of adhesives in the last 50 years, and when most people are experimenting, they're not usually chemically astute and tend to simply be creating garbage soup.  In the forum where I read about these 'creations', they were using things like orange juice (acidic, with sugar), ground dog kibble (oil and food products), sawdust, etc.

And let me point out to newcomers, that I am separating the building of a project from the surface decoration of it.  With surface decoration, you have a lot more freedom of expression, and the number of materials is much wider.  You can use many things on the surface that you would never use in the construction of your project.  Who know, maybe ground dog food, applied to the surface of a PM dog, would be just perfect.  I would advise sealing it, however, or it might end up as a vermin-attractant, or a chew-toy for a visiting pup.

"haecceity"... a new word!  Thanks!

Sue

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#15 2013-11-20 16:55:14

mavigogun
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From: Istanbul
Registered: 2009-04-22
Posts: 106

Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

A bit of clarification- because it seems I wasn't! MC may have a shorter initial set time than PVA (depending on how watered down the PVA), but doesn't it typically require more layers (compared to PVA) to retain coherence when wetted out with paint or additional layers of pulp/mache?  Puppet maker Mathieu Rene offered a recent example of a seemingly stable larger-than-life mask employing MC that began to collapse when painted;  the shell required additional layers/sealing (more time) to prevent deformation; Mathieu switched to acrylic for laminate additional strips.   I don't have much history with MC- so speak with no great authority -but the question of speed seems necessarily depended on application- including size, surface treatment, and just how much water is added to the adhesive, doesn't it?

As to the flexibility of PVA- that's dependent on temperature, proportion, age, and carrier.   The colder and older the PVA, the less ductile and more brittle; warm it sufficiently, it may melt before burning.   Very thin, "pure" PVA can be brittle- where as thick it ranges from "rubbery" to relatively inflexible.    Not all PVA is created equal, and the choice and amount of carrier (such as polyvinyl alcohol) makes a difference.

Laminating, I've created PVA-based parts with so plastic that it was an issue when tooling, while other pulp parts incorporating much more PVA -but also including a relatively small amount of filler (calcium carbonate)- have remarkably lower ductility.   One batch of pulp with a pulp-PVA-water ratio of 1/.5/.1 had no discernible plasticity- they broke before bending, and did not melt/stretch7deform when tooled.
   
"No adhesive is perfect for all uses or projects.  That's why you need to explore the limitations of each one individually."

Ain't that the truth!   

"...a lot of money has been poured into knowledge and development of adhesives in the last 50 years..."

I'm painfully aware of how out-of-touch I am to that knowledge base- in part, that's why I come here and seek wisdom from the likes of Sue!   The mention of citric acid, certain oils, and sugars in the form of orange juice is a great example of where insight would be of great help, as acids, oils, and sugars have all played parts in past mache recipes.   I LOVE the dog food example!   Reminiscent of pulp recipes that include milled grain or bread, dog food may contain some other appropriate constituents besides flours- such as collagen, oils that impact the working or dry character of pulp, and calcium carbonate.   Of course, not all dog food is created equal; a successful recipe would be brand specific!   An educated creator is at a huge advantage when reading the ingredient list and crude breakdown on a bag of dog food.   Lamb-and-rice or corn-and-poultry-digest?   As an adhesive, rice has much to recommend it over corn, me thinks...


In this age where people-made things are more common ingredients than what nature provided, a creative vocabulary that incorporates materials native to our (often more urban) environment IS natural- a synthesis, paper, is our foundation, after all!   Ever wonder what could be had with a mixture of a powdered schedule 4 recycled plastic, pulp paper, and the application of heat?   I do.

Last edited by mavigogun (2013-11-20 18:33:42)

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#16 2013-11-20 18:37:03

dopapier
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Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

Blimey!  What are you guys on?  Don't forget that cow dung can be excellent in some building structures, so perhaps it is an ingredient we shouldn't ignore???

CMC is not quick drying at all, however thick you make it.  It works like any cellulose powder paste but does not have the animal/insect attracting qualities of edible compounds like rice, potato, tapioca etc. all of which can be turned into a sticky paste by boiling in water.


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#17 2013-11-20 21:29:30

CatPerson
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Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

"CMC is not quick drying at all, however thick you make it."

I have found that the thicker you make it, the longer it takes to dry, but I'm generally not into thick adhesives except for some attachments.  I make it the consistency of thin egg white.  The last time I used it, I was making an almost-human-sized skull, and by the time I finished the second half, the first part was dry.  And, of course, I didn't add any PVA to it, David.  ;-)

As to additives, I try to keep things simple, not complicate them.  My poor little ADD-afflicted brain can't take the stress, much less remember what I added before I took that drink of water.

Cow dung?  I don't have any of that.  I've got lots of cat, dog, duck and chicken dung, but for some strange reason, I hesitate to include it.

Sue

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#18 2013-11-20 22:50:17

mavigogun
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From: Istanbul
Registered: 2009-04-22
Posts: 106

Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

"Don't forget that cow dung can be excellent in some building structures, so perhaps it is an ingredient we shouldn't ignore???"

It most certainly was employed during the 18th-19th century papier mache manufacturing Renaissance- and still IS in present-day India.   My source is an alpine meadow favoured by semi-sedentary shepherds; I'll visit in early spring, just after the snow melt, when all the active organic material has been depleted by 4 months of sun, wind, and frost.

Last edited by mavigogun (2013-11-20 23:05:29)

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#19 2013-11-21 10:33:06

dopapier
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Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

. . . and don't forget the cuckoos!!  smile)


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#20 2013-11-28 05:33:17

HLG
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Registered: 2013-10-21
Posts: 8

Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

Wow, reading all these replies is fascinating! Being able to discuss the various merits and drawbacks of all those different adhesives (and for there to be be no single, right answer) really does prove what an artform papier mache truly is.

Sorry I've been somewhat absent from this thread for a while - I've been ill and haven't been dealing with anything other than life's daily essentials.

The mannequin is nearing completion at the moment. I'm just sanding down the gesso to make it as smooth as possible before painting. It's suprisingly tricky as the texture of the gesso seems to 'catch' the surface of the sandpaper a tiny bit, making this awful squeaky noise! Do you think it's advisable to do another coat of gesso, and then sand again? Or should I just paint it after completing the sanding?

I was also wondering if you could make any recommendations as to whether I need to coat it in varnish or something to protect it? Ideally, I'd like to keep the surface matte (so it doesn't reflect light when photographed). I'm also wary of using anything with solvents in it, given that the armature is polystyrene (I'd hate to ruin it now!). Does papier mache always go mouldy if left unprotected?

Thanks, and best wishes,
HLG

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#21 2013-11-28 06:45:18

CatPerson
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From: Washington State, U.S.A.
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Posts: 1307

Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

Did you use an acrylic-based gesso?  If so, you could coat it with light coats of matte acrylic spray paint, which is compatible, and would be reasonably protective.  Light coats of the spray paint should be safe enough, with several coats of materials between the finish and the polystyrene, and the speed at which they dry.  There is a kind of spray paint here in the U.S. with the brand name of Design Master, which can be used directly on plastic foam, but I really don't think you need to go to that.  Liquid paints would be more of a danger.  Also, if you used an acrylic spray paint, you could keep a can or two bought at the same time (hopefully same dye lot) for touch-ups if needed.


True shellac is the only non-toxic sealing material that I know about.  Shellac is made from the cocoon of the lac bug, dissolved in alcohol, so when the alcohol dissolves, it's non-toxic.  But it does have a glossy finish, although some people have used very fine steel wool on it to rub down the shine.  But that would be quite time-consuming, and might look funny if you didn't get it the same all over.

Sue

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#22 2013-12-06 05:53:19

HLG
Member
Registered: 2013-10-21
Posts: 8

Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

Hi,

Yes, I used store-bought acrylic gesso, and I also have a tube of white acrylic paint that I was planning to use. Why do you think liquid paints would be more of a danger? Or do you just mean non-acrylic liquid paints?

That's interesting about the shellac, but I agree that it could definitely look very strange if I sanded it with steel wool and it ended up uneven. I'd be really disappointed if that happened at this stage, so I don't think I'll risk it.

I've been looking around the internet for ideas, and I've noticed a few kinds of acrylic matte sealants, like this one: http://www.michaels.com/Spray-Acrylic-S … lt,pd.html

And I've also come across Krylon Clear Matte Sealer, with a couple of sites saying that's acrylic based too. I think I'd probably be more inclined to try the Krylon, as I haven't heard of the other brand and I don't know what sort of quality it would be.

Do you know if acrylic based products are always water based (and therefore safe for polystyrene)?

Thanks!
HLG

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#23 2013-12-07 00:58:30

CatPerson
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From: Washington State, U.S.A.
Registered: 2006-01-09
Posts: 1307

Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

I was thinking liquid solvent-based paints, not acrylics.  Sometimes my brain works faster than my fingers; other times, it’s the other way around.

Practically any kind of paint can be used on PM, I was thinking of the damage a solvent-based one could do to your polystyrene – if there was an uncovered gap, it might seep through.  But if it’s well-covered with PM, it probably wouldn’t be an issue.

“Do you know if acrylic based products are always water based (and therefore safe for polystyrene)?

I have never known of an acrylic glue or paint that wasn’t water-based.  Check the clean-up instructions – if it’s soap/water cleanup, it’s water-based.

Sue

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#24 2013-12-09 10:32:18

mavigogun
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From: Istanbul
Registered: 2009-04-22
Posts: 106

Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

"True shellac is the only non-toxic sealing material that I know about..."

Tree resins, waxes, and linseed oil on the raw-ingredient side, a variety of relatively new bio-resins- some in the form of epoxy -on the highly-processed-from-organic-material-relatively-non-toxic-in-production-and-application side.

Check out bio resins here:

http://www.entropyresins.com/products
http://www.cambridge-biopolymers.com/Bioresin.htm

A bunch of water-based (low VOC) binders of several sorts here:

http://www.jesmonite.co.uk/system/

And a water-based "eco-friendly" acrylic here:

http://www.jesmonite.co.uk/system/

With the demand for the properties of bio resins on the rise, expect to see much more of them- with greater ease of access and falling prices.

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#25 2013-12-09 19:36:34

CatPerson
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From: Washington State, U.S.A.
Registered: 2006-01-09
Posts: 1307

Re: Wrinkles/air bubbles developed in papier mache after applying gesso...

"Non-toxic" was the operative term here.  I didn't check them all, just the first two items on the first link, but their Material Safety & Data Sheets (MSDS) didn't indicate that they were non-toxic, precautions still have to be taken.

As cynical as I am, I would say that any "new and exciting/different" chemical substances are highly likely to require care in use.  They may be less dangerous than prior substances, but I would doubt that most, if any, are non-toxic.  It's difficult (if not impossible) to produce a proprietary formula with natural materials.  And money is the name of the game.

Sue

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