Jump to content

If you're one of the gradually reducing number of folks that aren't currently receiving notifications to topics you've subscribed to, or PMs you're receiving, first check you've got the correct address in your profile, then drop in and post your experience in this thread, remembering to tell us your email provider's details, which is the part after the @ in your email address.

This site uses cookies! Learn More

This site uses cookies!

You can find a list of those cookies here: mysite.com/cookies

By continuing to use this site, you agree to allow us to store cookies on your computer. :)

Sign in to follow this  
Nutsabout

Air drying clay, problems.

Recommended Posts

I tried to use air dry clay from Hobbycraft to make a diorama base,  but after it dried overnight it has multiple cracks.

Was I using the wrong product, or using the wrong technique? 

Thoughts please.

Thanks 

Ian..

Share this post


Link to post
Share on other sites

How thick were you putting it on, and what was it on?

 

I've found it helps to spread a thin layer of PVA and apply the clay onto that to help adhesion - then if it cracks it won't come away and you can fill the cracks with more clay (or a slip of clay and water.) Thin layers are much less likely to crack.

 

You can also brush the dried clay with a PVA/water mix to seal it and stop it dusting.

 

HTH,

 

Will

Share this post


Link to post
Share on other sites
2 hours ago, Will Vale said:

How thick were you putting it on, and what was it on?

 

I've found it helps to spread a thin layer of PVA and apply the clay onto that to help adhesion - then if it cracks it won't come away and you can fill the cracks with more clay (or a slip of clay and water.) Thin layers are much less likely to crack.

 

You can also brush the dried clay with a PVA/water mix to seal it and stop it dusting.

 

HTH,

 

Will

Thanks Will,

 

It was on a hardboard backing for a picture frame, I did give the board a coat of PVA first and let that dry.

The thickness was mainly 1-2mm to max of about 5mm in places. but it cracked all over, not just the thicker parts. 

I have tried filling the cracks with slip but where I made track marks etc it looks awful. 

The clay seemed very wet out of the pack, would letting it dry out a bit first help reduce shrinkage?  

 

Assuming I get the base looking ok, would you advise sealing it with PVA before painting or would the paint seal it sufficiently?

 

Ian..

 

 

Share this post


Link to post
Share on other sites

That doesn't sound like an excessively thick layer, although I'm pretty sure I had similar problems making a base on a picture frame once. I'll see if I can find if I wrote anything down.

 

On the sealing, I think the PVA is worth it and will probably save you some paint. The dry clay is quite thirsty.

 

Will

 

 

Share this post


Link to post
Share on other sites

I've had nothing but bad luck with air dry clay.  The high humidity found where I live gives it fits. Have you tried Sculpey? As long as you don't over bake it, it's always worked for me. It's really cheap as well.

Share this post


Link to post
Share on other sites

Is it possible that the material that the clay has been applied to has moved, possibly after having absorbed water from the clay itself? Any movement seems the most likely source of the clay cracking....

 

Hope this is of some help.

 

Chris.  

Edited by spruecutter96
Correcting a typo.

Share this post


Link to post
Share on other sites
17 hours ago, Will Vale said:

That doesn't sound like an excessively thick layer, although I'm pretty sure I had similar problems making a base on a picture frame once. I'll see if I can find if I wrote anything down.

 

On the sealing, I think the PVA is worth it and will probably save you some paint. The dry clay is quite thirsty.

 

Will

 

 

I will definitely seal the clay before painting, good point, thanks Will.

 

17 hours ago, Thud4444 said:

I've had nothing but bad luck with air dry clay.  The high humidity found where I live gives it fits. Have you tried Sculpey? As long as you don't over bake it, it's always worked for me. It's really cheap as well.

I'll try Sculpey next time, thanks. 

 

4 hours ago, spruecutter96 said:

Is it possible that the material that the clay has been applied to has moved, possibly after having absorbed water from the clay itself? Any movement seems the most likely source of the clay cracking....

 

Hope this is of some help.

 

Chris.  

Possibly, the base was just the cheep hardboard from the back of a picture frame, so although I sealed it with PVA it could have absorbed some water & then dried out.

 

Thanks for your thoughts guys, I really appreciate your time. I think I will strip it off and start again.

Ian..

Share this post


Link to post
Share on other sites

No problem at all, Ian. 

 

I hope the second attempt is much more successful for you. 

 

Cheers.

 

Chris. 

Share this post


Link to post
Share on other sites

The cracking is simply the clay shrinking as the water evaporates out of it.

Sculpey or Fimo is ok, but it has its draw backs, like having to bake it at 130* for 30 minutes or so - can the base be baked?

I now use the tile grout from a £1 shop. Put on in thin layers it doesn't crack and is dry inside a couple of hours

Share this post


Link to post
Share on other sites
2 hours ago, Black Knight said:

The cracking is simply the clay shrinking as the water evaporates out of it.

Sculpey or Fimo is ok, but it has its draw backs, like having to bake it at 130* for 30 minutes or so - can the base be baked?

I now use the tile grout from a £1 shop. Put on in thin layers it doesn't crack and is dry inside a couple of hours

Thanks, might give that a go, but cost might be prohibitive :)

Share this post


Link to post
Share on other sites

Using such a thin hardboard base seems to me to be a major factor.... it will expand and warp with the moisture from the clay, then shrink and move again as it dries.

Rather than waste what you may have left, try it on a chipboard base of 1cm thick. You can always find a deep picture frame and make the chipboard base to fit.

 

If the thicker base doesn't work then refer to advice given above.

Rearguards,

Badder

 

Share this post


Link to post
Share on other sites
7 hours ago, Badder said:

Using such a thin hardboard base seems to me to be a major factor.... it will expand and warp with the moisture from the clay, then shrink and move again as it dries.

Rather than waste what you may have left, try it on a chipboard base of 1cm thick. You can always find a deep picture frame and make the chipboard base to fit.

 

If the thicker base doesn't work then refer to advice given above.

Rearguards,

Badder

 

Thanks Badder,

Looking at the base again, after calming down a bit, I think your right, the cheep hardboard does seem water damaged.

 

Ian.. 

Share this post


Link to post
Share on other sites

Have you considered something less porous such as acrylic / styrene / corex / foamex sheeting - not massively expensive and available in a range of thicknesses - just a thought.

Share this post


Link to post
Share on other sites

I regularly use air drying clay and have not had cracking problem (but not used on hardboard).  

 

As other have advised, I first seal and surface (I often place over cardboard) with PVA to stop it pulling moisture out of the clay too quick.

 

Once it is dry I recoat with PVA to hold clay.

 

Don't let it dry out too quick such as in centrally heated house - I place out in garage and in summer place cloth over the top to slow evaporation.

 

Paul

 

 

Share this post


Link to post
Share on other sites
14 hours ago, dcrfan said:

I regularly use air drying clay and have not had cracking problem (but not used on hardboard).  

 

As other have advised, I first seal and surface (I often place over cardboard) with PVA to stop it pulling moisture out of the clay too quick.

 

Once it is dry I recoat with PVA to hold clay.

 

Don't let it dry out too quick such as in centrally heated house - I place out in garage and in summer place cloth over the top to slow evaporation.

 

Paul

 

 

Thanks Paul, I'll try again.

Ian..

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

×