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beetee
03-21-2014, 11:26 AM
I am total newbie in acrylic,(i mostly use charcoal and some oil painting),my question -- is GAC 100 a unique product? or is there an equivalent in other brands?
,that I could use (for sealing MDF etc And for using in acrylic paintings)

Thanks in advance

Brian

janinco
03-21-2014, 01:45 PM
Ampersand mentions Gamblin PVA on their blog:
http://ampersandartsupply.blogspot.com/2012/09/panel-painting-tips-how-to-seal.html

Jan

beetee
03-21-2014, 02:32 PM
Thanks Jan.
I am looking for an equivalent or alternative to GAC100 which can be used for saeling and used for a medium while painting?

Brian

janinco
03-21-2014, 02:55 PM
I'm using Daler Rowney's white gesso primer and really like it. I haven't used it on MDF, just birch panel, but I think it covers well. I keep a squirt bottle to use instead of titanium white when I'm building a light opaque area over darker paints.

This is what the product description says:
"Can be used on any non oily surface eg.Plywood, untempered hardboard, cardboard, plaster, MDF, canvas, etc."

It's considered student grade so it's for use indoors only and I use 3-4 coats with light sanding between if it's for canvas and a quick pass between coats with a razor blade if it's board and I'm trying to get a very smooth surface. I suppose a higher priced, artist grade product would cover better and require fewer coats, but I'm still learning and need something that isn't terribly expensive. I paid $24 for a gallon tub on sale.

Jan

lt_scout
03-21-2014, 04:45 PM
You could use plain old carpender's glue like Weldbond mixed with a bit of water for sealing your panels, works great. It would NOT work as a medium.

Using any brand acrylic polymer gel would work as medium. It's the same binder as acrylic paint without the pigment added. Pick one that has the flow you like. You could even seal with it but you run the risk of wood tannins getting through, wood glue is better.

idylbrush
03-21-2014, 04:48 PM
i believe GAC 100 is a proprietary product. Golden Artists Colors = GAC. I am not aware of any other product that makes the same claims. I use either GAC 100 or 700 myself.

beetee
03-21-2014, 06:28 PM
Big thanks to all.Bryan Jan and Idly:thumbsup:

It sound like GAC 100 is the only one that can be used to seal and as a medium.
I thought there might have been an alternative :(

Thanks again

Brian

janinco
03-21-2014, 07:02 PM
Brian, Golden has a great information page on preparing a support if you haven't seen it:
http://www.goldenpaints.com/technicaldata/prepsupp.php

There's a table at the bottom of the page for rigid supports.

Look forward to seeing your acrylic paintings!

Jan

beetee
03-21-2014, 09:15 PM
That's a great link Jan thanks.


My acrylic painting- that's a whole different story':eek:

Cheers
Brian

Aspsusa
03-25-2014, 04:08 AM
Using any brand acrylic polymer gel would work as medium. It's the same binder as acrylic paint without the pigment added. Pick one that has the flow you like.

This.
GAC 100 is really just a plain acrylic polymer emulsion - Golden reps usually say that it is the plainest acrylic they sell, and more or less the form of acrylic that all their products start out as before being modified (consistency, pigment, handling characteristics, drying properties, etc).

If you read through tons of Golden tech sheets (as I do because I'm a nerd, and I sell Golden in a tiny shop and try to know as much as I can), you'll notice that very often GAC100 and Soft Gel Gloss thinned with water (at 2:1) are recommended more or less interchangeably when it comes to isolation layers.
(Presumably because Soft Gel Gloss is more versatile for people who want just a tad more structure in a medium. The gels and mediums are also a bit easier to handle than the GACs, as they foam less.)

You could even seal with it but you run the risk of wood tannins getting through, wood glue is better.

This is interesting, I've been thinking about "wood glue" (which I take to be PVAs), and possible negative/positive aspects of using that in place of an acrylic isolation layer.
Could you elucidate on why you feel a PVA is better as a sealant/isolation layer? And if there's anything special to look out for when choosing a PVA-glue?

Aspsusa
03-25-2014, 04:10 AM
Triple posted. Ignore (any mod with the power, please delete).

Aspsusa
03-25-2014, 04:13 AM
Double post, WC seems to have the hiccups this morning, ignore

beetee
03-26-2014, 06:32 PM
Thank you for all the replies-still confused.

Can anyone name me an alternative to GAC100 -which I can use to seal panels AND as a medium.
Is for example Winsor & Newton Matt Medium a similar product?

Cheers
Brian

Aspsusa
03-29-2014, 05:31 AM
Thank you for all the replies-still confused.

Can anyone name me an alternative to GAC100 -which I can use to seal panels AND as a medium.
Is for example Winsor & Newton Matt Medium a similar product?


Since no one else has taken this on...

I don't have any personal experience with W&N acrylic mediums (or at least not any recent experience), but *in principle* any acrylic emulsion can be considered "similar" for this purpose.

EXCEPT one snag: anything matte over an absorbent surface runs a slight risk of resulting in a weirdly frosted surface.
This is because "matte" means there are _particles_ suspended in the emulsion (I always beg people to be cautious with anything matte; you can always add matte, but you can never take it away), and it is theoretically possible that the acrylic part of the medium would sink into the substrate, but leave the matting agents sitting on top, unevenly at worst.

If I had a big tub of matte medium sitting around and was all out of GAC100 (or any other "clean" acrylic) I'd definitely test it.
(In fact I think I have put some kind of matte medium directly on an old piece of birch veneer for testing purposes; looked and felt quite nice. But a) haven't actually used it, and b) I have no illusions of it being archival or long lasting.)

I'd say just test it.


But I'm still interested in the view that PVAs (ie woodglues) might be a better choice than acrylics as an initial isolation layer...