The appraisal identifies and values the artwork
Detail of vessel by Toots Zynsky, showing fused glass threads


The Value of Glass offers appraisal services for those seeking insurance or charitable tax donation appraisals, and for appraisers requiring advice. Decades of experience as well as an extensive computerized database and archival library of images and texts form an unparalleled basis for establishing and supporting values. The appraisal practice is limited to glass of the modern era, specifically: Studio and contemporary glass, Louis C. Tiffany, Emile Gallé and Venetian glass.

William Warmus prepares the appraisals. He is an experienced appraiser, the author of 10 books, a past curator at The Corning Museum of Glass, and former editor of Glass magazine. Mr. Warmus curated the landmark New Glass exhibition of contemporary glass that traveled to The Metropolitan Museum of Art and he has over twenty years of appraisal experience in the field of modern glass. See his resume on this web site for details at resume.

"Warmus’ credentials are bulletproof—he was the curator of the Corning Museum of Glass, was the editor of Glass magazine, and has written books on the biggest names in glass art, from Rene Lalique to Dale Chihuly. Although his expertise extends far beyond the realm of glass art into the broader study of art, there is little that happens in the medium that he cannot speak to in an eloquent and informed way."

Chris Peterson, reviewing "Fire and Form" in Glass Craftsman at:



For a brief market overview for studio glass, follow this link: Studio Glass Market Analysis

Appraisals can be done on site or sometimes through the mail by photographs. If the appraiser decides that an on site review is required, he can sometimes suggest a qualified appraiser near the collector's home who can conduct the appraisal, thus saving travel expenses. Collectors may also want to use the appraisal service as a second opinion, in order to add strength or credibility to an existing appraisal. We are not a member of the American Society of Appraisers or the American Association of Appraisers. If a collector prefers to use a member of one of these organizations, we may be able to help suggest one.

Credentials of the Appraiser

IRS publication 561 has this to say about the qualifications of appraisers (excerpted):

Opinions of Experts

"Generally, the weight given to an expert's
opinion on matters such as the authenticity
of a coin or a work of art, or the most profit-
able and best use of a piece of real estate,
depends on the knowledge and competence
of the expert and the thoroughness with which
the opinion is supported by experience and

"The weight given an appraisal depends
on the completeness of the report, the quali-
fications of the appraiser, and the appraiser's
demonstrated knowledge of the donated
property. An appraisal must give all the facts
on which to base an intelligent judgment of
the value of the property.

The appraisal will not be given much
weight if:

1) All the factors that apply are not consid-
2) The opinion is not supported with facts,
such as purchase price and comparable
sales, or
3) The opinion is not consistent with known

The appraiser's opinion is never more
valid than the facts on which it is based;
without these facts it is simply a guess.
Membership in professional appraisal or
dealer organizations does not automatically
establish the appraiser's competency.
Nor does the lack of certificates, memberships,
etc., automatically disprove the competency
of the appraiser."


Conduct of the Appraisal

Guidelines for professional conduct are well established in the field of appraisals. It is our opinion that appraisers should meet at least the following minimum criteria:

1-Professional and Ethical

Collectors seeking appraisals should ascertain that the individual or organization selected is well qualified through experience in the field and that they are aware of and follow established appraisal practices such as Uniform Standard of Appraisal Practices. Appraisers should not act in such a way that they damage the reputation of other qualified appraisers who follow established professional guidelines. The reasoning of the appraisal document should be detailed and include an explanation of how the value was determined.

2-Accurate and Confidential

While recognizing that appraisals are a matter of informed opinion and that the value of an object is only determined when or if it is sold, appraisers have a duty to their clients to provide accurate numerical values based upon careful research and analysis. The appraiser should protect the confidentiality of the material prepared for the client, unless otherwise authorized.

3-No conflicts of interest

Appraisal fees should not be based upon a percentage of the final appraised value or contingent upon a court settlement. If the appraiser has a possible interest in the material being appraised (as a possible agent for sale of the material, for example) this interest should be disclosed and approved by the client.

Is the appraiser also a dealer? Does this pose a possible conflict of interest? In general, the tax law prevents dealers who sold objects to collectors from appraising those objects to support charitable tax deductions. While there are good appraisers who are also dealers, collectors should be sure that dealer-appraisers certify and describe any financial dealings they have had concerning the artworks or artists being appraised, as well as the extent of any future interest in selling the artwork. William Warmus Inc. is not a gallery or dealer in art. On occasion, we may negotiate a small broker fee (never above 3%) if asked to locate a dealer for a specific artwork, but we do not actively seek such business.

4-A complete report

The appraisal report should include the following: A detailed description of the material appraised and the market in which it is situated; the objectives to be achieved; limitations of the process (if any); the appraisal method used; the kind of value to be established (insurance; tax); analysis of the material and a determination of its value (including authenticity, condition, comparable values from auction records, etc.); the credentials of the appraiser; a disclosure of any interest on behalf of the appraiser; the signature of the appraiser and of any others who have provided essential assistance with the appraisal.


For more information:

For our rates, click here: Rates

For resume, click here: Resume

For information about insuring a collection, click here: Insurance


Contact information:

William Warmus Inc.     The Value of Glass

PO Box 30 Lansing    New York     14882

Fax and voice mail     877-574-6833

E-mail www@warmus.com


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The appraisal identifies and values the artwork