rejuvinating old tube acrylic paint?

[PaintByNumbers]

A comment in another thread reminds me -- I have old Liquitex tube paint that would cost many $$$ to replace. It has separated and gotten gritty. Is there an effective way to rejuvinate it?

[Joe Kutz]

Yes.

 

I've heard it done in a couple different ways - though the only way I have ever done it myself is to squeeze it all out into a container for inspection and reconstitution. You will then need a container for permanent storage of the paint once you are done (I like to use the glass Testor's mixing bottles for that). You may need to carefully cut the tube open in order to get to it.

 

Take a look at the paint in your temporary container for discolorations as well as large pieces of dried binder or solidified pigment. If the pigment as actually separated and not dried with the binder...it should fall to pieces with gentle pressure - if it is harder than that though, it is less an issue of separation and more an issue of drying out. Dried out paint requires a fair amount of work and materials to reconstitute...so unless the color is OOP - you might consider buying a new tube.

 

Separated pigment with Good binder: Take a short length of brass rod and bend the end into a few curly cues. Nothing special, but if you can get it to look a bit like a dough hook...that seems to work well enough. They make a few different store versions of that tool...but I tend to just use the rod. Anywho, chuck the rod into a dremel and on low speed mix the pigment and binder back together again. You will likely want to add a small amount of a PEG based acrylic thinner to both prevent the paint from drying while you work and also lubricate the pigment in order to achieve a better consistency with less work. If you notice that the binder is thicker than what it should be - but still fluid and not crusty, use an acrylic medium to help get things to the proper consistency. I try to use a medium from the same company in order to avoid potential interactions (not all acrylics are the same resin...).

 

Separated pigment with Dried Binder: This happens from time to time. The binder itself slowly dries, but for one reason or another the pigment remains in good condition. Remove any chunks of dried acrylic that you can. If it hasn't fully separated - you will need to go a bit further than simply picking at the chunks. Quite often I will use a fluid to separate out the pigment from the binder via either centrifuge or gravity. Without the centrifuge you can mix an inert fluid (I like to use ethanol...although not truly inert, it has certain benefits) with the dried binder and pigment. Mix it up really really well and then let it sit for a day or three covered so that the liquid can't evaporate out. You will want to use as tall and narrow of a container as you have available (I use centrifuge cones...but you can normally get test tubes cheap from a variety of sources). Once it has sat for awhile (or taken a ride in the centrifuge) you will be able to see three or more layers in the tube. One will of course be the liquid, one will be the pigment(s) and one will be the binder. Most likely you will see several layers in the pigment area - since most paints use several pigments and other solids to get the coverage/color in question. You can carefully use a pipette to either work your way down to the pigment layer...or simply remove the pigments from the bottom directly. Slow and steady is the key, you do not want to disturb the layers you are not working with.

 

Once you have the pigments separated, simply add a clear acrylic of your desired consistency (liquid, gels...something in between) to them...give it a good mix and repackage. Again, for mixing, I like to use the Dremel. If the pigments have a chance to dry, they can be a bugger to get mixed back up by hand. The dremel makes short work of things though.

 

Dried Up Mess: For most people, just buy a new tube...again, unless it is an OOP color. For this you will need to use a mortar and pestle to reduce the chunks to a fine powder. Don't worry that you are grinding up binder. It will not change the actual color much at all...however it does tend to act as a matting agent. Once you have a fine powder, add the binder as mentioned above.

 

You can achieve the exact same consistency as the original by using various additives and mediums that are available...however, more often than not - I choose to go ahead and convert it to my preferred consistency right away. This allows me to work straight from the bottle in the future.

[PaintByNumbers]

>

Separated pigment with Good binder: Take a short length of brass rod and bend the end into a few curly cues. Nothing special, but if you can get it to look a bit like a dough hook

>

 

That's kinda what I figured, but I don't want to whip air into it... wonder if I could make up a corkscrew that would fit into the tube itself; it would be easier than rebottling it.

[Joe Kutz]

That's kinda what I figured, but I don't want to whip air into it... wonder if I could make up a corkscrew that would fit into the tube itself; it would be easier than rebottling it.

 

As long as you keep the corkscrew in the paint itself (as opposed to half in and half out) you will introduce a minimal amount of air. If you want to try it in the tube itself (that is one of the ways I have never done...but supposedly it does work) be careful about what the tube itself is made out of...and make sure you bend the end of the corkscrew back up so that it won't scrape the tube.

 

Many of the older tubes are made out of a very soft metal like lead foil - and can easily be damaged...either working the lead into the paint or puncturing the tube itself.