diff --git a/orsopy/slddb/blender.py b/orsopy/slddb/blender.py
new file mode 100644
index 0000000..357c9b7
--- /dev/null
+++ b/orsopy/slddb/blender.py
@@ -0,0 +1,136 @@
+"""
+Pure calculation functions for combining biological sequences and material blends.
+No web-framework dependencies.
+"""
+
+from .dbconfig import DB_FILE
+from .database import SLDDB
+from .material import Material
+from .element_table import get_element
+from .comparators import ExactString
+
+AMINO_ABRV = {
+    "A": "Alanine",
+    "R": "Arginine",
+    "N": "Asparagine",
+    "D": "Aspartate",
+    "B": "Aspartate",
+    "C": "Cysteine",
+    "E": "Glutamate",
+    "Q": "Glutamine",
+    "Z": "Glutamate",
+    "G": "Glycine",
+    "H": "Histidine",
+    "I": "Isoleucine",
+    "L": "Leucine",
+    "K": "Lysine",
+    "M": "Methionine",
+    "F": "Phenylalanine",
+    "P": "Proline",
+    "S": "Serine",
+    "T": "Threonine",
+    "W": "Tryptophan",
+    "Y": "Tyrosine",
+    "V": "Valine",
+}
+
+RNA_ABRV = {
+    "A": "RNA-Adenine",
+    "G": "RNA-Guanine",
+    "C": "RNA-Cytosine",
+    "U": "RNA-Uracil",
+}
+
+DNA_ABRV = {
+    "A": "DNA-Adenine",
+    "G": "DNA-Guanine",
+    "C": "DNA-Cytosine",
+    "T": "DNA-Thymine",
+}
+
+
+class SequenceParseError(ValueError):
+    pass
+
+
+def clean_str(string):
+    return string.replace('\n', '').replace('\r', '').replace('\t', '').replace(' ', '').strip()
+
+
+hx2o = Material([(get_element(element), amount) for element, amount in [('Hx', 2.0), ('O', 1.0)]], dens=1.0)
+
+
+def collect_combination(ids, name_dict):
+    db = SLDDB(DB_FILE)
+    elements: list[Material] = []
+    loaded_ids: dict[str, Material] = {}
+    for id in ids:
+        if id not in loaded_ids:
+            try:
+                entry = db.search_material(name=ExactString(name_dict[id]))[0]
+            except KeyError:
+                possible_ids = name_dict.keys()
+                raise SequenceParseError(f"Not a valid identifier {id}, options are {''.join(possible_ids)}")
+            except IndexError:
+                raise SequenceParseError(f"Molecule {name_dict[id]} not found in database")
+            m = db.select_material(entry)
+            loaded_ids[id] = m
+        elements.append(loaded_ids[id])
+    result = elements[0]
+    for element in elements[1:]:
+        result += element
+    return result
+
+
+def collect_protein(acids):
+    acids = clean_str(acids).upper()
+    result = collect_combination(acids, AMINO_ABRV) + hx2o
+    result.extra_data['description'] = f'protein - {len(acids)} residues'
+    return result
+
+
+def collect_dna(bases):
+    bases = clean_str(bases).upper()
+    result = collect_combination(bases, DNA_ABRV) + hx2o
+    result.extra_data['description'] = f'DNA - {len(bases)} residues'
+    return result
+
+
+def collect_rna(bases):
+    bases = clean_str(bases).upper()
+    result = collect_combination(bases, RNA_ABRV) + hx2o
+    result.extra_data['description'] = f'RNA - {len(bases)} residues'
+    return result
+
+
+def collect_blendIDs(formula):
+    db = SLDDB(DB_FILE)
+    elements: list[Material] = []
+    loaded_ids = {}
+    items = []
+    while '(' in clean_str(formula):
+        pre, formula = formula.split(')', 1)
+        number = float(pre.split('*', 1)[0].strip('(').strip())
+        ID = int(pre.split('*', 1)[1].strip())
+        items.append((number, ID))
+    for number, ID in items:
+        if ID not in loaded_ids:
+            entry = db.search_material(ID=ID)[0]
+            m = db.select_material(entry)
+            loaded_ids[ID] = m
+        elements.append(number * loaded_ids[ID])
+    result = elements[0]
+    for element in elements[1:]:
+        result += element
+    return result
+
+
+def collect_blend(mtype, idstr):
+    if mtype == 'protein':
+        return collect_protein(idstr)
+    elif mtype == 'dna':
+        return collect_dna(idstr)
+    elif mtype == 'rna':
+        return collect_rna(idstr)
+    elif mtype == 'db':
+        return collect_blendIDs(idstr)
diff --git a/orsopy/slddb/tests/test_webapi.py b/orsopy/slddb/tests/test_webapi.py
index aaffc21..ae6ffd6 100644
--- a/orsopy/slddb/tests/test_webapi.py
+++ b/orsopy/slddb/tests/test_webapi.py
@@ -86,7 +86,7 @@ def test_a_downloaddb(self):
         if not self.server_available:
             return
         # make sure the path of the module is correct and that the database has not been downloaded
-        self.assertTrue(api.first_access)
+        self.assertTrue(api.update_db)
         # self.assertEqual(slddb.__file__, os.path.join(self.path, 'slddb', '__init__.py'))
         self.assertFalse(os.path.exists(slddb.DB_FILE))
         # test of database download
@@ -115,26 +115,26 @@ def test_a_downloaddb(self):
     def test_b_check(self):
         if not self.server_available:
             return
-        api.first_access = True
+        api.update_db = True
         if os.path.isfile(slddb.DB_FILE):
             os.remove(slddb.DB_FILE)
         api.check()
-        self.assertFalse(api.first_access)
-        api.first_access = True
+        self.assertFalse(api.update_db)
+        api.update_db = True
         api.check()
-        self.assertFalse(api.first_access)
+        self.assertFalse(api.update_db)
         api.check()
         # check the update case
         api.db.db.close()
         del api.db
-        api.first_access = True
+        api.update_db = True
         api.max_age = -1
         api.check()
         api.max_age = 1
         # check warning if download url doesn't work during update
         api.db.db.close()
         del api.db
-        api.first_access = True
+        api.update_db = True
         api.max_age = -1
 
         from orsopy.slddb import dbconfig, webapi
diff --git a/orsopy/slddb/webapi.py b/orsopy/slddb/webapi.py
index 6facd54..22e8f11 100644
--- a/orsopy/slddb/webapi.py
+++ b/orsopy/slddb/webapi.py
@@ -9,7 +9,8 @@
 from urllib.error import URLError
 
 from . import DB_FILE, SLDDB
-from .dbconfig import WEBAPI_URL
+from .dbconfig import WEBAPI_URL, DB_MATERIALS_FIELDS, DB_MATERIALS_HIDDEN_DATA, db_lookup
+from .blender import collect_protein, collect_dna, collect_rna
 from .element_table import get_element
 from .material import Formula, Material
 
@@ -46,13 +47,13 @@ class SLD_API:
     max_age = 1
     db: SLDDB = None
 
-    def __init__(self):
-        self.first_access = True
-        self.use_webquery = True  # only try webquery once, if error occurs switch to local database
+    def __init__(self, update_db=True):
+        self.update_db = update_db
+        self.use_webquery = False  # default to using local database, which is updated regularly
 
     def check(self):
         # make sure the local database file is up to date, if not try to download newest version
-        if self.first_access:
+        if self.update_db:
             now = datetime.datetime.now()
             try:
                 stat = pathlib.Path(DB_FILE).stat()
@@ -70,7 +71,7 @@ def check(self):
                     except URLError as err:
                         warnings.warn("Can't download new version of database; " + str(err))
             self.db = SLDDB(DB_FILE)  # after potential update, make connection with local database
-            self.first_access = False
+            self.update_db = False
         else:
             return
 
@@ -95,11 +96,7 @@ def webquery(qdict):
         return json.loads(webdata.read())  # return decoded data
 
     def localquery(self, qdict):
-        return self.db.search_material(**qdict)
-
-    def localmaterial(self, ID):
-        res = self.db.search_material(ID=ID)
-        return self.db.select_material(res[0])
+        return query_api(qdict)
 
     def search(self, **opts):
         """
@@ -130,29 +127,22 @@ def material(self, ID):
             material=api.material(res[0]['ID'])
             print(material.dens, material.rho_n, material.f_of_E(8.0))
         """
-        if not self.use_webquery:
-            return self.localmaterial(ID)
 
-        self.check()
-        try:
-            res = self.webquery({"ID": int(ID)})
-        except URLError:
-            self.use_webquery = False
-            return self.localmaterial(ID)
-        else:
-            f = Formula(res["formula"], sort=False)
-            mat_data = dict(dens=float(res["density"]), ID=ID, extra_data={})
-            if res.get("name", None):
-                mat_data["name"] = res["name"]
-            if res.get("mu", 0.0):
-                mat_data["mu"] = res["mu"]
-            elif res.get("M", 0.0):
-                mat_data["M"] = res["M"]
-            for key in ["ORSO_validated", "description", "doi", "reference"]:
-                if key in res:
-                    mat_data["extra_data"][key] = res[key]
-            out = Material([(get_element(element), amount) for element, amount in f], **mat_data)
-            return out
+        res = self.search(ID=int(ID))
+
+        f = Formula(res["formula"], sort=False)
+        mat_data = dict(dens=float(res["density"]), ID=ID, extra_data={})
+        if res.get("name", None):
+            mat_data["name"] = res["name"]
+        if res.get("mu", 0.0):
+            mat_data["mu"] = res["mu"]
+        elif res.get("M", 0.0):
+            mat_data["M"] = res["M"]
+        for key in ["ORSO_validated", "description", "doi", "reference"]:
+            if key in res:
+                mat_data["extra_data"][key] = res[key]
+        out = Material([(get_element(element), amount) for element, amount in f], **mat_data)
+        return out
 
     @staticmethod
     def custom(formula, dens=None, fu_volume=None, rho_n=None, mu=0.0, xsld=None, xE=None):
@@ -180,7 +170,7 @@ def bio_blender(self, sequence, molecule="protein"):
         Get material for protein, DNA or RNA. Provide a letter sequence and molecule type ('protein', 'dna', 'rna').
         """
         opts = {molecule.lower(): sequence, "sldcalc": "true"}
-        res = self.webquery(opts)
+        res = self.search(**opts)
         mat_data = dict(fu_volume=float(res["fu_volume"]), name=f"BioBlender-{molecule.lower()}", extra_data={})
         for key in [
             "description",
@@ -190,3 +180,113 @@ def bio_blender(self, sequence, molecule="protein"):
 
         out = Material(Formula(res["formula"]), **mat_data)
         return out
+
+
+# webquery API functions:
+def calc_api(args):
+    """Calculate SLD from formula/density or biological sequence.
+
+    args: dict-like with optional keys: formula, density, protein, dna, rna,
+          name, material_description, xray_unit.
+    Returns a JSON string.
+    """
+    if 'protein' in args:
+        try:
+            material = collect_protein(args['protein'])
+        except Exception as e:
+            return repr(e)
+        else:
+            name = args.get('name', 'protein')
+    elif 'dna' in args:
+        try:
+            material = collect_dna(args['dna'])
+        except Exception as e:
+            return repr(e)
+        else:
+            name = args.get('name', 'DNA')
+    elif 'rna' in args:
+        try:
+            material = collect_rna(args['rna'])
+        except Exception as e:
+            return repr(e)
+        else:
+            name = args.get('name', 'RNA')
+    elif 'formula' in args and 'density' in args:
+        f = Formula(args['formula'], sort=False)
+        try:
+            material = Material(f, dens=float(args['density']))
+        except Exception as e:
+            return repr(e)
+        else:
+            name = args.get('name', 'User Query')
+    else:
+        return 'Could not calculate, missing formula and density or protein/dna/rna sequence'
+    material.name = name
+    if args.get('material_description', '') != '':
+        material.extra_data['description'] = args['material_description']
+    out = material.export(xray_units=args.get('xray_unit', 'edens'))
+    return out
+
+
+def select_api(args):
+    """Return JSON for a material selected by ID.
+
+    args: dict-like with keys: ID, and optionally xray_unit.
+    Returns a JSON string.
+    """
+    db = SLDDB(DB_FILE)
+    res = db.search_material(filter_invalid=False, ID=int(args['ID']))
+    try:
+        material = db.select_material(res[0])
+    except IndexError:
+        return '## ID not found in database'
+    except Exception as e:
+        return repr(e) + '<br >' + "Raised when tried to parse material = %s" % res[0]
+    out = material.export(xray_units=args.get('xray_unit', 'edens'))
+    return out
+
+
+def search_api(args):
+    """Search the database with the given field values.
+
+    args: dict-like mapping DB field names to query values.
+    Returns a JSON string.
+    """
+    query = {}
+    for key, value in args.items():
+        if str(value).strip() == '':
+            continue
+        if key in DB_MATERIALS_FIELDS:
+            try:
+                query[key] = db_lookup[key][1].convert(str(value))
+            except Exception as e:
+                return repr(e) + '<br >' + "Raised when tried to parse %s = %s" % (key, value)
+    db = SLDDB(DB_FILE)
+    res = db.search_material(serializable=True, limit=10000, **query)
+
+    # remove hidden database fields besides ORSO validation
+    for ri in res:
+        for field in DB_MATERIALS_HIDDEN_DATA:
+            if field.startswith('validated'):
+                continue
+            del ri[field]
+
+    return res
+
+
+def query_api(args):
+    """Dispatch an API request based on which keys are present in args.
+
+    args: dict-like (e.g. request.args or a plain dict).
+    Returns a JSON string.
+    """
+    if 'ID' in args:
+        return select_api(args)
+    elif 'sldcalc' in args:
+        return calc_api(args)
+    elif 'get_fields' in args:
+        return [
+            field for field in DB_MATERIALS_FIELDS if field not in DB_MATERIALS_HIDDEN_DATA
+        ]
+    else:
+        return search_api(args)