best hard glaze or varnish for a gypsum plaster vase

[davemm1779]

Hi everyone,

I currently work with gypsum plaster (Crystacal R) creating ceramic pieces for the home such as vases (to be used with artificial flowers). The issue I have had for a long time is finding a hard glaze or varnish so as to stop the item from scratching. Whilst the plaster itself is very hard, it can scratch fairly easily, so I have to sell my pieces with a warning to look after with care. If acrylic painting over it then scratches are even more noticeable. I've been looking for gloss varnishes or something similar that can give a hard shell finish, and that is safe to use and don't contain any harmful toxins as most of my work is done indoors at home. I've tried a number of varnishes on the market but have had poor results. These seem to be more useful for protecting artwork than ceramics. They don't stop scuffs and light scratches. The best I've come across is Decoart (duraclear varnish), but this is an American product with very few resellers in the UK. It is also quite difficult to apply. If done incorrectly, you end up with a milky patch that doesn't dry clear and you end up ruining the whole piece. On occasions I've also been able to pick the varnish off once dry.

I recently came across Rustins clear glaze which I understand is for clay pieces which are then fired but I've heard it can be used on plaster as well. This seems to be the ideal thing but I don't fire my plaster no do I need to, so would Rustin's only work on fired items?

Is there anything that maybe more suitable for plaster items that can provide a hard shell gloss finish similar to a glazed effect and that doesn't yellow over time?

Any help greatly appreciated.

[Bill Kielb]

From my reading Rustins is a clear acrylic water borne product that air drys quickly. From my experience with coatings they will have a finished hardness. I would google and compare urethanes, epoxies and maybe even plain old lacquer. It’s been used as an auto finish for many years and when buffed may end up hardest and most resistant.

This product says they are the hardest https://www.cerakote.com/news/65/cerakote-introduces-the-worlds-strongest-clear-coat

My suggestion - Google I think will net some things to try. 

Edited May 11, 2022 by Bill Kielb

[Chilly]

2 hours ago, davemm1779 said:

Rustins clear glaze which I understand is for clay pieces which are then fired

This is applied to fired pieces.  It is not for firing, it would just burn off.

 

Are you using the plaster to create moulds, or using the plaster as the finished item?  If the latter, you probably won't find many answers here, as the definition of ceramics is: 

made of clay and permanently hardened by heat. "a ceramic bowl". https://www.google.com/search?q=ceramic+meaning&rlz=1C1CHBF_en-GBGB953GB953&oq=ceramic+mea&aqs=chrome.0.0i512l2j69i57j0i512l7.8885j1j7&sourceid=chrome&ie=UTF-8

 

Bill's suggestion is probably as much as any of us know.  Some of us do work with plaster, but for moulds not final use.

[Mark C.]

From reading the OPs post it looks as though the work is plaster not ceramic

so I suggest an epoxy coating to add strength to the plaster.

[PeterH]

Flier on painting plaster at https://justpaint.org/painting-plaster-with-acrylics-2/

Note: Before painting plaster, it is important to allow the material to become fully dry. This process may take up to a month, so follow the plaster manufacturer’s recommendations on curing time. Ultimately, the plaster needs to be very dry in order for the initial priming layers to properly bond to the plaster surface.

[neilestrick]

Have you looked in to other types of plaster to see if there is something is more scratch resistant than what you're using?

[Callie Beller Diesel]

How easy is it for you to obtain  marine grade products, or perhaps automotive finishes?

Edited:

Scratch that. You said you were working in your home. Neither of those categories are remotely non-toxic.

[Jeff Longtin]

Years ago I had a client whose primary business was casting plaster/cement statuary.  They had a huge roto-casting device that allowed them to cast cement table bases essentially hollow. 

One other thing that caught my attention was that they had a huge drying room for drying the statuary.  It had a heater, a fan, and a dehumidifier. I thought it was to dry slip casting molds. (The molds I made for them.) But they said no, it was primarily to dry the cement ware they were producing.

In another part of the shop they had a work area where customers could come in and paint the various cement objects with a variety of paints and sealers..  It was never mentioned that scratching was an issue so I wonder if "completely dry" is the solution to your problem?